Iacutone.rb

coding and things

Sidekiq and Carrierwave, Part 3

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I decided to use the Carrierwave Backgrounder Gem in order to asynchronously upload photos to Amazon S3. This is a different gem than the one Ryan Bates uses in his Railscast. I was having difficulty implimenting the Carrierwave Direct Gem However, the Backgrounder Gem works great! This is the last installment of the three part series on uploading photos.

This is the final version of the avatar_uploader.rb file. Just add line 3, which is in the Backgrounder documentaion.

avatar_uploader.rb lang: ruby
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  class AvatarUploader < CarrierWave::Uploader::Base
  # include CarrierWaveDirect::Uploader
  include ::CarrierWave::Backgrounder::Delay

  # Include RMagick or MiniMagick support:
  include CarrierWave::RMagick
  # include CarrierWave::MiniMagick

  # Include the Sprockets helpers for Rails 3.1+ asset pipeline compatibility:
  include Sprockets::Helpers::RailsHelper
  include Sprockets::Helpers::IsolatedHelper

  # Choose what kind of storage to use for this uploader:
  # storage :file
  storage :fog

  include CarrierWave::MimeTypes
  process :set_content_type

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  # def store_dir
  #   "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  # end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url
  #   # For Rails 3.1+ asset pipeline compatibility:
  #   # asset_path("fallback/" + [version_name, "default.png"].compact.join('_'))
  #
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  version :thumb do
    process :resize_to_limit => [150, 150]
  end

  version :profile do
    process :resize_to_limit => [200, 200]
  end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  # def extension_white_list
  #   %w(jpg jpeg gif png)
  # end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end
  end

Also, add this code to your model.

profile.rb
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 mount_uploader :avatar, AvatarUploader
  process_in_background :avatar

Following the install instructions, this file is created in the initializers directory.

initializers/carrierwave_backgrounder.rb
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 CarrierWave::Backgrounder.configure do |c|
    # c.backend :delayed_job, queue: :carrierwave
    # c.backend :resque, queue: :carrierwave
    c.backend :sidekiq, queue: :carrierwave
    # c.backend :girl_friday, queue: :carrierwave
    # c.backend :qu, queue: :carrierwave
    # c.backend :qc
  end

Then boot up Sidekiq to listen for jobs with sidekiq -q carrierwave command in your terminal. You might need to start your Redis server with the command redis-server. Your background worker should now asynchronously process background jobs!

Sidekiq also has a cool interface to show what workers are up, how many successes and failures there have been and some other neat features. It is real easy to set up. First add the following code to your Gemfile.

Gemfile
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 gem 'slim', '>= 1.1.0'
  gem 'sinatra', '>= 1.3.0', :require => nil

Then create this route with the require line before the beginning of the block.

routes.rb
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 require 'sidekiq/web'

  mount Sidekiq::Web => '/sidekiq'

I really like this gem and recommend it to anyone trying to run background processes to upload pictures via Carrierwave.

h/t Blake Johnson

Gon Gem

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I ran into difficulties trying to find a way to implement jQuery in a modal. It is not possible to use remote: true in a form_tag with Twitter Bootstrap. I successfully used the Gon Gem in order to remove elements from the DOM when an instance variable reached a certain number. If you find yourself in the position of needing to remove elements from a modal, this gem seems to be the way to go.

user_controller.rb
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    def create
      @user = User.new(params[:user])

      if @user.save

        @day_one_counter = []
        @day_one_counter = User.pluck(:time1)

        #@day_one_counter outputs an array of elements from the :time1 column. => ["11:00", "11:00", nil, nil, nil]

        b = Hash.new(0)

        @day_one_counter.each do |v|
          b[v] += 1
        end

        #the block increments the key/value pairs in the instantiated Hash. => {"11:00"=>2, nil=>3}

        @time1 = b["11:00"]
        gon.time1 = @time1

        #@time1 pulls out the value of the pair => 2
        #gon.time1 => 2, in order to use the @time1 instance variable in users.js

        @time2 = b["11:20"]
        gon.time2 = @time2

        @time3 = b["11:40"]
        gon.time3 = @time3

        render :time
      else
        render :new
      end
    end

This is a conintuation of the Pluck Method from my last blog post. For an overview of what is happening, read the comments provided above. With the gone.time1 variable, I can now use jQuery in my users.js file in order to remove elements from the DOM that go over a given number, in this case 5.

users.js
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   if (gon.time1 > 4) {
      $('.wrapper1').remove();
  }

  if (gon.time2 > 4) {
      $('.wrapper2').remove();
  }

...and the form

_time1.html.erb
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 <%= form_for @user do |f| %>
     <div class='wrapper1' id='pad'>11:00 A.M. <%= f.radio_button(:time1, '11:00') %><br /><%= 5 - @time1 unless @time1 == nil %> spots remaining.</div>
      <div class='wrapper2' id='pad'>11:20 A.M. <%= f.radio_button(:time1, '11:20') %><br /><%= 5 - @time2 unless @time2 == nil %> spots remaining.</div>
      <div class='wrapper'><%= f.radio_button(:time1, 'No time.') %>  Interested but not available during these times. Please inform me of future conversation opportunities.<br /></div>
 <%= f.hidden_field :day, :value => 'July 10' %>
 <button class="btn btn-inverse" type="submit"class="actions">Submit</button>
 <% end %>

Since the @time1 instance variable and therefore, gon.time1 are saved after my create action, the applicable time is > 4 if I want a total of 5 elements for a particular time on my :time1 column. The next time the modal is visited, the element will be removed!

I am so excited I found this gem and got my modal to work correctly! Also, a thanks for Railscast for the tutorial on the gem.

Passing Data to Javascript

Pluck Method in Active Record

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The past few days, I have been building a database to store some information for my friend Shari, a Peace Corps recruiter. The database includes, a name, email and phone number. Things got tricky building a date/time models and validations. Every given time has six time slots for a user to sign up. My conclusion to this problem was to create a different database column for every given time slot. Then, I used the pluck method on my Active Record database in order to turn all of my time columns into strings in an array. However, in Rails 3, pluck only excepts one column to turn into an array. This feature is being changed in Rails 4 according to this blog post where he describes how to tamper with the the Active Record library or create a module to provide a pluck_all method for a Rails 3 application. I implemented this code, and was returned an array of hashes which did not help my cause. But this is an interesting concept and it was fun and insightful reading the source code.

users_controller.rb
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  def create
    @user = User.new(params[:user])

    if @user.save

      @day_one_counter = []
      @day_one_counter = User.pluck(:time1)

      @day_two_counter = []
      @day_two_counter = User.pluck(:time2)

      b = Hash.new(0)
      c = Hash.new(0)

      @day_one_counter.each do |v|
        b[v] += 1
      end

      @day_two_counter.each do |v|
        c[v] += 1
      end

      @time1 = b["11:30"]
      @time2 = b["11:45"]
      @time3 = b["12:00"]
      @time4 = b["12:15"]
      @time5 = b["12:30"]
      @time6 = b["12:45"]
      @time7 = b["1:00"]
      @time8 = b["1:15"]
      @time9 = b["1:30"]
      @time10 = b["1:45"]
      @time11 = b["5:00"]
      @time12 = b["5:15"]
      @time13 = b["5:30"]
      @time14 = b["5:45"]
      @time15 = b["6:00"]
      @time16 = b["6:15"]
      @time17 = b["6:30"]
      @time18 = b["6:45"]
      @time19 = b["7:00"]
      @time20 = b["7:15"]

      @time21 = c["11:30"]
      @time22 = c["11:45"]
      @time23 = c["12:00"]
      @time24 = c["12:15"]
      @time25 = c["12:30"]
      @time26 = c["12:45"]
      @time27 = c["1:00"]
      @time28 = c["1:15"]
      @time29 = c["1:30"]
      @time30 = c["1:45"]
      @time31 = c["5:00"]
      @time32 = c["5:15"]
      @time33 = c["5:30"]
      @time34 = c["5:45"]
      @time35 = c["6:00"]
      @time36 = c["6:15"]
      @time37 = c["6:30"]
      @time38 = c["6:45"]
      @time39 = c["7:00"]
      @time40 = c["7:15"]

      # respond_to do |format|
      #   format.html
      #   format.js
      # end   

      render :time
    else
      render :new
    end
  end

This code gets really cumbersome the more time columns I add, so my next step is to DRY this shit up. But hell, it works and is going to make my friend's life easier, yay! for technology.

Using Impress.js With Rails

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I recently had an interview at an awesome creative agency, Canvas and wanted to show them something unique in order to make me stand out. I decided to build a thank you card with Impress.js. This is the thank you card I sent to their CTO. I enjoyed playing with Impress.js and will definitely incorporate it into many more applications in the future. However, there is not much documentation about how to get Impress to play nicely in a Rails app. The app was breaking in production, but working in development. The code following the impress.js file below specifies where to load the Javascript.

app/assets/javascripts/impress.js
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/**
 * impress.js
 *
 * impress.js is a presentation tool based on the power of CSS3 transforms and transitions
 * in modern browsers and inspired by the idea behind prezi.com.
 *
 *
 * Copyright 2011-2012 Bartek Szopka (@bartaz)
 *
 * Released under the MIT and GPL Licenses.
 *
 * ------------------------------------------------
 *  author:  Bartek Szopka
 *  version: 0.5.3
 *  url:     http://bartaz.github.com/impress.js/
 *  source:  http://github.com/bartaz/impress.js/
 */

/*jshint bitwise:true, curly:true, eqeqeq:true, forin:true, latedef:true, newcap:true,
         noarg:true, noempty:true, undef:true, strict:true, browser:true */

// You are one of those who like to know how thing work inside?
// Let me show you the cogs that make impress.js run...
(function ( document, window ) {
    'use strict';

    // HELPER FUNCTIONS

    // `pfx` is a function that takes a standard CSS property name as a parameter
    // and returns it's prefixed version valid for current browser it runs in.
    // The code is heavily inspired by Modernizr http://www.modernizr.com/
    var pfx = (function () {

        var style = document.createElement('dummy').style,
            prefixes = 'Webkit Moz O ms Khtml'.split(' '),
            memory = {};

        return function ( prop ) {
            if ( typeof memory[ prop ] === "undefined" ) {

                var ucProp  = prop.charAt(0).toUpperCase() + prop.substr(1),
                    props   = (prop + ' ' + prefixes.join(ucProp + ' ') + ucProp).split(' ');

                memory[ prop ] = null;
                for ( var i in props ) {
                    if ( style[ props[i] ] !== undefined ) {
                        memory[ prop ] = props[i];
                        break;
                    }
                }

            }

            return memory[ prop ];
        };

    })();

    // `arraify` takes an array-like object and turns it into real Array
    // to make all the Array.prototype goodness available.
    var arrayify = function ( a ) {
        return [].slice.call( a );
    };

    // `css` function applies the styles given in `props` object to the element
    // given as `el`. It runs all property names through `pfx` function to make
    // sure proper prefixed version of the property is used.
    var css = function ( el, props ) {
        var key, pkey;
        for ( key in props ) {
            if ( props.hasOwnProperty(key) ) {
                pkey = pfx(key);
                if ( pkey !== null ) {
                    el.style[pkey] = props[key];
                }
            }
        }
        return el;
    };

    // `toNumber` takes a value given as `numeric` parameter and tries to turn
    // it into a number. If it is not possible it returns 0 (or other value
    // given as `fallback`).
    var toNumber = function (numeric, fallback) {
        return isNaN(numeric) ? (fallback || 0) : Number(numeric);
    };

    // `byId` returns element with given `id` - you probably have guessed that ;)
    var byId = function ( id ) {
        return document.getElementById(id);
    };

    // `$` returns first element for given CSS `selector` in the `context` of
    // the given element or whole document.
    var $ = function ( selector, context ) {
        context = context || document;
        return context.querySelector(selector);
    };

    // `$$` return an array of elements for given CSS `selector` in the `context` of
    // the given element or whole document.
    var $$ = function ( selector, context ) {
        context = context || document;
        return arrayify( context.querySelectorAll(selector) );
    };

    // `triggerEvent` builds a custom DOM event with given `eventName` and `detail` data
    // and triggers it on element given as `el`.
    var triggerEvent = function (el, eventName, detail) {
        var event = document.createEvent("CustomEvent");
        event.initCustomEvent(eventName, true, true, detail);
        el.dispatchEvent(event);
    };

    // `translate` builds a translate transform string for given data.
    var translate = function ( t ) {
        return " translate3d(" + t.x + "px," + t.y + "px," + t.z + "px) ";
    };

    // `rotate` builds a rotate transform string for given data.
    // By default the rotations are in X Y Z order that can be reverted by passing `true`
    // as second parameter.
    var rotate = function ( r, revert ) {
        var rX = " rotateX(" + r.x + "deg) ",
            rY = " rotateY(" + r.y + "deg) ",
            rZ = " rotateZ(" + r.z + "deg) ";

        return revert ? rZ+rY+rX : rX+rY+rZ;
    };

    // `scale` builds a scale transform string for given data.
    var scale = function ( s ) {
        return " scale(" + s + ") ";
    };

    // `perspective` builds a perspective transform string for given data.
    var perspective = function ( p ) {
        return " perspective(" + p + "px) ";
    };

    // `getElementFromHash` returns an element located by id from hash part of
    // window location.
    var getElementFromHash = function () {
        // get id from url # by removing `#` or `#/` from the beginning,
        // so both "fallback" `#slide-id` and "enhanced" `#/slide-id` will work
        return byId( window.location.hash.replace(/^#\/?/,"") );
    };

    // `computeWindowScale` counts the scale factor between window size and size
    // defined for the presentation in the config.
    var computeWindowScale = function ( config ) {
        var hScale = window.innerHeight / config.height,
            wScale = window.innerWidth / config.width,
            scale = hScale > wScale ? wScale : hScale;

        if (config.maxScale && scale > config.maxScale) {
            scale = config.maxScale;
        }

        if (config.minScale && scale < config.minScale) {
            scale = config.minScale;
        }

        return scale;
    };

    // CHECK SUPPORT
    var body = document.body;

    var ua = navigator.userAgent.toLowerCase();
    var impressSupported =
                          // browser should support CSS 3D transtorms 
                           ( pfx("perspective") !== null ) &&

                          // and `classList` and `dataset` APIs
                           ( body.classList ) &&
                           ( body.dataset ) &&

                          // but some mobile devices need to be blacklisted,
                          // because their CSS 3D support or hardware is not
                          // good enough to run impress.js properly, sorry...
                           ( ua.search(/(iphone)|(ipod)|(android)/) === -1 );

    if (!impressSupported) {
        // we can't be sure that `classList` is supported
        body.className += " impress-not-supported ";
    } else {
        body.classList.remove("impress-not-supported");
        body.classList.add("impress-supported");
    }

    // GLOBALS AND DEFAULTS

    // This is were the root elements of all impress.js instances will be kept.
    // Yes, this means you can have more than one instance on a page, but I'm not
    // sure if it makes any sense in practice ;)
    var roots = {};

    // some default config values.
    var defaults = {
        width: 1024,
        height: 768,
        maxScale: 1,
        minScale: 0,

        perspective: 1000,

        transitionDuration: 1000
    };

    // it's just an empty function ... and a useless comment.
    var empty = function () { return false; };

    // IMPRESS.JS API

    // And that's where interesting things will start to happen.
    // It's the core `impress` function that returns the impress.js API
    // for a presentation based on the element with given id ('impress'
    // by default).
    var impress = window.impress = function ( rootId ) {

        // If impress.js is not supported by the browser return a dummy API
        // it may not be a perfect solution but we return early and avoid
        // running code that may use features not implemented in the browser.
        if (!impressSupported) {
            return {
                init: empty,
                goto: empty,
                prev: empty,
                next: empty
            };
        }

        rootId = rootId || "impress";

        // if given root is already initialized just return the API
        if (roots["impress-root-" + rootId]) {
            return roots["impress-root-" + rootId];
        }

        // data of all presentation steps
        var stepsData = {};

        // element of currently active step
        var activeStep = null;

        // current state (position, rotation and scale) of the presentation
        var currentState = null;

        // array of step elements
        var steps = null;

        // configuration options
        var config = null;

        // scale factor of the browser window
        var windowScale = null;

        // root presentation elements
        var root = byId( rootId );
        var canvas = document.createElement("div");

        var initialized = false;

        // STEP EVENTS
        //
        // There are currently two step events triggered by impress.js
        // `impress:stepenter` is triggered when the step is shown on the 
        // screen (the transition from the previous one is finished) and
        // `impress:stepleave` is triggered when the step is left (the
        // transition to next step just starts).

        // reference to last entered step
        var lastEntered = null;

        // `onStepEnter` is called whenever the step element is entered
        // but the event is triggered only if the step is different than
        // last entered step.
        var onStepEnter = function (step) {
            if (lastEntered !== step) {
                triggerEvent(step, "impress:stepenter");
                lastEntered = step;
            }
        };

        // `onStepLeave` is called whenever the step element is left
        // but the event is triggered only if the step is the same as
        // last entered step.
        var onStepLeave = function (step) {
            if (lastEntered === step) {
                triggerEvent(step, "impress:stepleave");
                lastEntered = null;
            }
        };

        // `initStep` initializes given step element by reading data from its
        // data attributes and setting correct styles.
        var initStep = function ( el, idx ) {
            var data = el.dataset,
                step = {
                    translate: {
                        x: toNumber(data.x),
                        y: toNumber(data.y),
                        z: toNumber(data.z)
                    },
                    rotate: {
                        x: toNumber(data.rotateX),
                        y: toNumber(data.rotateY),
                        z: toNumber(data.rotateZ || data.rotate)
                    },
                    scale: toNumber(data.scale, 1),
                    el: el
                };

            if ( !el.id ) {
                el.id = "step-" + (idx + 1);
            }

            stepsData["impress-" + el.id] = step;

            css(el, {
                position: "absolute",
                transform: "translate(-50%,-50%)" +
                           translate(step.translate) +
                           rotate(step.rotate) +
                           scale(step.scale),
                transformStyle: "preserve-3d"
            });
        };

        // `init` API function that initializes (and runs) the presentation.
        var init = function () {
            if (initialized) { return; }

            // First we set up the viewport for mobile devices.
            // For some reason iPad goes nuts when it is not done properly.
            var meta = $("meta[name='viewport']") || document.createElement("meta");
            meta.content = "width=device-width, minimum-scale=1, maximum-scale=1, user-scalable=no";
            if (meta.parentNode !== document.head) {
                meta.name = 'viewport';
                document.head.appendChild(meta);
            }

            // initialize configuration object
            var rootData = root.dataset;
            config = {
                width: toNumber( rootData.width, defaults.width ),
                height: toNumber( rootData.height, defaults.height ),
                maxScale: toNumber( rootData.maxScale, defaults.maxScale ),
                minScale: toNumber( rootData.minScale, defaults.minScale ),
                perspective: toNumber( rootData.perspective, defaults.perspective ),
                transitionDuration: toNumber( rootData.transitionDuration, defaults.transitionDuration )
            };

            windowScale = computeWindowScale( config );

            // wrap steps with "canvas" element
            arrayify( root.childNodes ).forEach(function ( el ) {
                canvas.appendChild( el );
            });
            root.appendChild(canvas);

            // set initial styles
            document.documentElement.style.height = "100%";

            css(body, {
                height: "100%",
                overflow: "hidden"
            });

            var rootStyles = {
                position: "absolute",
                transformOrigin: "top left",
                transition: "all 0s ease-in-out",
                transformStyle: "preserve-3d"
            };

            css(root, rootStyles);
            css(root, {
                top: "50%",
                left: "50%",
                transform: perspective( config.perspective/windowScale ) + scale( windowScale )
            });
            css(canvas, rootStyles);

            body.classList.remove("impress-disabled");
            body.classList.add("impress-enabled");

            // get and init steps
            steps = $$(".step", root);
            steps.forEach( initStep );

            // set a default initial state of the canvas
            currentState = {
                translate: { x: 0, y: 0, z: 0 },
                rotate:    { x: 0, y: 0, z: 0 },
                scale:     1
            };

            initialized = true;

            triggerEvent(root, "impress:init", { api: roots[ "impress-root-" + rootId ] });
        };

        // `getStep` is a helper function that returns a step element defined by parameter.
        // If a number is given, step with index given by the number is returned, if a string
        // is given step element with such id is returned, if DOM element is given it is returned
        // if it is a correct step element.
        var getStep = function ( step ) {
            if (typeof step === "number") {
                step = step < 0 ? steps[ steps.length + step] : steps[ step ];
            } else if (typeof step === "string") {
                step = byId(step);
            }
            return (step && step.id && stepsData["impress-" + step.id]) ? step : null;
        };

        // used to reset timeout for `impress:stepenter` event
        var stepEnterTimeout = null;

        // `goto` API function that moves to step given with `el` parameter (by index, id or element),
        // with a transition `duration` optionally given as second parameter.
        var goto = function ( el, duration ) {

            if ( !initialized || !(el = getStep(el)) ) {
                // presentation not initialized or given element is not a step
                return false;
            }

            // Sometimes it's possible to trigger focus on first link with some keyboard action.
            // Browser in such a case tries to scroll the page to make this element visible
            // (even that body overflow is set to hidden) and it breaks our careful positioning.
            //
            // So, as a lousy (and lazy) workaround we will make the page scroll back to the top
            // whenever slide is selected
            //
            // If you are reading this and know any better way to handle it, I'll be glad to hear about it!
            window.scrollTo(0, 0);

            var step = stepsData["impress-" + el.id];

            if ( activeStep ) {
                activeStep.classList.remove("active");
                body.classList.remove("impress-on-" + activeStep.id);
            }
            el.classList.add("active");

            body.classList.add("impress-on-" + el.id);

            // compute target state of the canvas based on given step
            var target = {
                rotate: {
                    x: -step.rotate.x,
                    y: -step.rotate.y,
                    z: -step.rotate.z
                },
                translate: {
                    x: -step.translate.x,
                    y: -step.translate.y,
                    z: -step.translate.z
                },
                scale: 1 / step.scale
            };

            // Check if the transition is zooming in or not.
            //
            // This information is used to alter the transition style:
            // when we are zooming in - we start with move and rotate transition
            // and the scaling is delayed, but when we are zooming out we start
            // with scaling down and move and rotation are delayed.
            var zoomin = target.scale >= currentState.scale;

            duration = toNumber(duration, config.transitionDuration);
            var delay = (duration / 2);

            // if the same step is re-selected, force computing window scaling,
            // because it is likely to be caused by window resize
            if (el === activeStep) {
                windowScale = computeWindowScale(config);
            }

            var targetScale = target.scale * windowScale;

            // trigger leave of currently active element (if it's not the same step again)
            if (activeStep && activeStep !== el) {
                onStepLeave(activeStep);
            }

            // Now we alter transforms of `root` and `canvas` to trigger transitions.
            //
            // And here is why there are two elements: `root` and `canvas` - they are
            // being animated separately:
            // `root` is used for scaling and `canvas` for translate and rotations.
            // Transitions on them are triggered with different delays (to make
            // visually nice and 'natural' looking transitions), so we need to know
            // that both of them are finished.
            css(root, {
                // to keep the perspective look similar for different scales
                // we need to 'scale' the perspective, too
                transform: perspective( config.perspective / targetScale ) + scale( targetScale ),
                transitionDuration: duration + "ms",
                transitionDelay: (zoomin ? delay : 0) + "ms"
            });

            css(canvas, {
                transform: rotate(target.rotate, true) + translate(target.translate),
                transitionDuration: duration + "ms",
                transitionDelay: (zoomin ? 0 : delay) + "ms"
            });

            // Here is a tricky part...
            //
            // If there is no change in scale or no change in rotation and translation, it means there was actually
            // no delay - because there was no transition on `root` or `canvas` elements.
            // We want to trigger `impress:stepenter` event in the correct moment, so here we compare the current
            // and target values to check if delay should be taken into account.
            //
            // I know that this `if` statement looks scary, but it's pretty simple when you know what is going on
            // - it's simply comparing all the values.
            if ( currentState.scale === target.scale ||
                (currentState.rotate.x === target.rotate.x && currentState.rotate.y === target.rotate.y &&
                 currentState.rotate.z === target.rotate.z && currentState.translate.x === target.translate.x &&
                 currentState.translate.y === target.translate.y && currentState.translate.z === target.translate.z) ) {
                delay = 0;
            }

            // store current state
            currentState = target;
            activeStep = el;

            // And here is where we trigger `impress:stepenter` event.
            // We simply set up a timeout to fire it taking transition duration (and possible delay) into account.
            //
            // I really wanted to make it in more elegant way. The `transitionend` event seemed to be the best way
            // to do it, but the fact that I'm using transitions on two separate elements and that the `transitionend`
            // event is only triggered when there was a transition (change in the values) caused some bugs and 
            // made the code really complicated, cause I had to handle all the conditions separately. And it still
            // needed a `setTimeout` fallback for the situations when there is no transition at all.
            // So I decided that I'd rather make the code simpler than use shiny new `transitionend`.
            //
            // If you want learn something interesting and see how it was done with `transitionend` go back to
            // version 0.5.2 of impress.js: http://github.com/bartaz/impress.js/blob/0.5.2/js/impress.js
            window.clearTimeout(stepEnterTimeout);
            stepEnterTimeout = window.setTimeout(function() {
                onStepEnter(activeStep);
            }, duration + delay);

            return el;
        };

        // `prev` API function goes to previous step (in document order)
        var prev = function () {
            var prev = steps.indexOf( activeStep ) - 1;
            prev = prev >= 0 ? steps[ prev ] : steps[ steps.length-1 ];

            return goto(prev);
        };

        // `next` API function goes to next step (in document order)
        var next = function () {
            var next = steps.indexOf( activeStep ) + 1;
            next = next < steps.length ? steps[ next ] : steps[ 0 ];

            return goto(next);
        };

        // Adding some useful classes to step elements.
        //
        // All the steps that have not been shown yet are given `future` class.
        // When the step is entered the `future` class is removed and the `present`
        // class is given. When the step is left `present` class is replaced with
        // `past` class.
        //
        // So every step element is always in one of three possible states:
        // `future`, `present` and `past`.
        //
        // There classes can be used in CSS to style different types of steps.
        // For example the `present` class can be used to trigger some custom
        // animations when step is shown.
        root.addEventListener("impress:init", function(){
            // STEP CLASSES
            steps.forEach(function (step) {
                step.classList.add("future");
            });

            root.addEventListener("impress:stepenter", function (event) {
                event.target.classList.remove("past");
                event.target.classList.remove("future");
                event.target.classList.add("present");
            }, false);

            root.addEventListener("impress:stepleave", function (event) {
                event.target.classList.remove("present");
                event.target.classList.add("past");
            }, false);

        }, false);

        // Adding hash change support.
        root.addEventListener("impress:init", function(){

            // last hash detected
            var lastHash = "";

            // `#/step-id` is used instead of `#step-id` to prevent default browser
            // scrolling to element in hash.
            //
            // And it has to be set after animation finishes, because in Chrome it
            // makes transtion laggy.
            // BUG: http://code.google.com/p/chromium/issues/detail?id=62820
            root.addEventListener("impress:stepenter", function (event) {
                window.location.hash = lastHash = "#/" + event.target.id;
            }, false);

            window.addEventListener("hashchange", function () {
                // When the step is entered hash in the location is updated
                // (just few lines above from here), so the hash change is 
                // triggered and we would call `goto` again on the same element.
                //
                // To avoid this we store last entered hash and compare.
                if (window.location.hash !== lastHash) {
                    goto( getElementFromHash() );
                }
            }, false);

            // START 
            // by selecting step defined in url or first step of the presentation
            goto(getElementFromHash() || steps[0], 0);
        }, false);

        body.classList.add("impress-disabled");

        // store and return API for given impress.js root element
        return (roots[ "impress-root-" + rootId ] = {
            init: init,
            goto: goto,
            next: next,
            prev: prev
        });

    };

    // flag that can be used in JS to check if browser have passed the support test
    impress.supported = impressSupported;

})(document, window);

// NAVIGATION EVENTS

// As you can see this part is separate from the impress.js core code.
// It's because these navigation actions only need what impress.js provides with
// its simple API.
//
// In future I think about moving it to make them optional, move to separate files
// and treat more like a 'plugins'.
(function ( document, window ) {
    'use strict';

    // throttling function calls, by Remy Sharp
    // http://remysharp.com/2010/07/21/throttling-function-calls/
    var throttle = function (fn, delay) {
        var timer = null;
        return function () {
            var context = this, args = arguments;
            clearTimeout(timer);
            timer = setTimeout(function () {
                fn.apply(context, args);
            }, delay);
        };
    };

    // wait for impress.js to be initialized
    document.addEventListener("impress:init", function (event) {
        // Getting API from event data.
        // So you don't event need to know what is the id of the root element
        // or anything. `impress:init` event data gives you everything you 
        // need to control the presentation that was just initialized.
        var api = event.detail.api;

        // KEYBOARD NAVIGATION HANDLERS

        // Prevent default keydown action when one of supported key is pressed.
        document.addEventListener("keydown", function ( event ) {
            if ( event.keyCode === 9 || ( event.keyCode >= 32 && event.keyCode <= 34 ) || (event.keyCode >= 37 && event.keyCode <= 40) ) {
                event.preventDefault();
            }
        }, false);

        // Trigger impress action (next or prev) on keyup.

        // Supported keys are:
        // [space] - quite common in presentation software to move forward
        // [up] [right] / [down] [left] - again common and natural addition,
        // [pgdown] / [pgup] - often triggered by remote controllers,
        // [tab] - this one is quite controversial, but the reason it ended up on
        //   this list is quite an interesting story... Remember that strange part
        //   in the impress.js code where window is scrolled to 0,0 on every presentation
        //   step, because sometimes browser scrolls viewport because of the focused element?
        //   Well, the [tab] key by default navigates around focusable elements, so clicking
        //   it very often caused scrolling to focused element and breaking impress.js
        //   positioning. I didn't want to just prevent this default action, so I used [tab]
        //   as another way to moving to next step... And yes, I know that for the sake of
        //   consistency I should add [shift+tab] as opposite action...
        document.addEventListener("keyup", function ( event ) {
            if ( event.keyCode === 9 || ( event.keyCode >= 32 && event.keyCode <= 34 ) || (event.keyCode >= 37 && event.keyCode <= 40) ) {
                switch( event.keyCode ) {
                    case 33: // pg up
                    case 37: // left
                    case 38: // up
                             api.prev();
                             break;
                    case 9:  // tab
                    case 32: // space
                    case 34: // pg down
                    case 39: // right
                    case 40: // down
                             api.next();
                             break;
                }

                event.preventDefault();
            }
        }, false);

        // delegated handler for clicking on the links to presentation steps
        document.addEventListener("click", function ( event ) {
            // event delegation with "bubbling"
            // check if event target (or any of its parents is a link)
            var target = event.target;
            while ( (target.tagName !== "A") &&
                    (target !== document.documentElement) ) {
                target = target.parentNode;
            }

            if ( target.tagName === "A" ) {
                var href = target.getAttribute("href");

                // if it's a link to presentation step, target this step
                if ( href && href[0] === '#' ) {
                    target = document.getElementById( href.slice(1) );
                }
            }

            if ( api.goto(target) ) {
                event.stopImmediatePropagation();
                event.preventDefault();
            }
        }, false);

        // delegated handler for clicking on step elements
        document.addEventListener("click", function ( event ) {
            var target = event.target;
            // find closest step element that is not active
            while ( !(target.classList.contains("step") && !target.classList.contains("active")) &&
                    (target !== document.documentElement) ) {
                target = target.parentNode;
            }

            if ( api.goto(target) ) {
                event.preventDefault();
            }
        }, false);

        // touch handler to detect taps on the left and right side of the screen
        // based on awesome work of @hakimel: https://github.com/hakimel/reveal.js
        document.addEventListener("touchstart", function ( event ) {
            if (event.touches.length === 1) {
                var x = event.touches[0].clientX,
                    width = window.innerWidth * 0.3,
                    result = null;

                if ( x < width ) {
                    result = api.prev();
                } else if ( x > window.innerWidth - width ) {
                    result = api.next();
                }

                if (result) {
                    event.preventDefault();
                }
            }
        }, false);

        // rescale presentation when window is resized
        window.addEventListener("resize", throttle(function () {
            // force going to active step again, to trigger rescaling
            api.goto( document.querySelector(".step.active"), 500 );
        }, 250), false);

    }, false);

})(document, window);

// THAT'S ALL FOLKS!
//
// Thanks for reading it all.
// Or thanks for scrolling down and reading the last part.
//
// I've learnt a lot when building impress.js and I hope this code and comments
// will help somebody learn at least some part of it.

Add this to the directory listed above. At the time of this writing, this is new newest realease of Impress.js. In order to get Impress and Rails to cooperate, I changed my application.html.erb file to this:

view/layouts/application.erb
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<!DOCTYPE html>
<html>
<head>
  <title>Thanksyou</title>
  <%= stylesheet_link_tag    "application", :media => "all" %>
  <%= javascript_include_tag "application" %>
  <%= csrf_meta_tags %>
  <link href='http://fonts.googleapis.com/css?family=Questrial' rel='stylesheet' type='text/css'>
</head>
<body>
 
<%= yield %>

<%= javascript_include_tag "application" %>
</body>
</html>

That is pretty much it, however I ran into difficulty determining where and when to load the impress.js file. I tried moving it into several different directories including the index view with both the javascript_include_tag and the script tag. I also messed with the load order of the application.js asset pipeline. After fretting for far too long, I put the file in the correct place and all was well. I hope this post saves someone whom wants to play with Impress.js time and energy.

Also, the tutorial is very well written and worth reading for anyone that wants to use this library.

Client Side Validations

| Comments

The Railscast for the Client Side Validations Gem is very outdated and does not function. Furthermore, the documentation for the gem did not completely work with my version of Rails, 3.2.13. The point of this post is to get front end validations to work with Rails 3.2.13.

gem ‘client_side_validations’

$ rails g client_side_validations:install

The file below is created, but you must uncomment lines 10 through 16 in order to get it to work.

config/initializers/client_side_validations.rb
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# ClientSideValidations Initializer

# Uncomment to disable uniqueness validator, possible security issue
# ClientSideValidations::Config.disabled_validators = [:uniqueness]

# Uncomment to validate number format with current I18n locale
# ClientSideValidations::Config.number_format_with_locale = true

# Uncomment the following block if you want each input field to have the validation messages attached.
ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  unless html_tag =~ /^<label/
    %{<div class="field_with_errors">#{html_tag}<label for="#{instance.send(:tag_id)}" class="message">#{instance.error_message.first}</label></div>}.html_safe
  else
    %{<div class="field_with_errors">#{html_tag}</div>}.html_safe
  end
end

//= require rails.validations
...in applications.js
...and the following to your form.

_form.html.erb
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<%= form_for @user, :validate => true do |f| %>


And a little CSS...


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.field_with_errors .message {
  color: #FFC200;
  padding-left: 10px;
  display: inline;
}

Your app should now be able to display Rails error messages in line with your form fields. This is where I began to run into problems, creating a custom validator.


The Github Documentation says to put the following code into app/validators/email_validator.rb


initializers/email_validator.rb
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class EmailValidator < ActiveModel::EachValidator
  def validate_each(record, attr_name, value)
    unless value =~ /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i
      record.errors.add(attr_name, :email, options.merge(:value => value))
    end
  end
end

# This allows us to assign the validator in the model
module ActiveModel::Validations::HelperMethods
  def validates_email(*attr_names)
    validates_with EmailValidator, _merge_attributes(attr_names)
  end
end

This did not work for me. However, creating the email_validator.rb file under the initializers directory did the trick. I need to ask a Flatiron School compadre why this is. Follow the rest of the custom validator documentation for awesome validations. I hope this saves people time while implenting this gem.

Amazon S3, Part 2

| Comments

So we have Carrierwave uploading pictures to our local server. Perhaps we want the pictures stored on a third party cloud provider. Amazon S3 and Carrierwave work very well together. This blog post describes how to upload your pictures to the Amazon S3 cloud. Again, thanks to Ryan Bates and Railscasts for the great information.

In order to upload files to Amazon S3, we will be using the Fog Gem. The Carrierwave gem handles the Fog interaction with Amazon S3 behind the scenes.

  • Sign up for an Amazon AWS account.
  • Create a S3 bucket to store your files (photos)
  • Input your credentials in:
initializers/carrierwave.rb
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CarrierWave.configure do |config|
  config.fog_credentials = {
    :provider               => 'AWS',
    :aws_access_key_id      => ENV['AWS_ACCESS_KEY_ID'],
    :aws_secret_access_key  => ENV['AWS_SECRET_ACCESS_KEY']
  }
  config.fog_directory  = ENV['AWS_S3_BUCKET']
end

I put my ENV variables in the Figaro Gem.

You also need to modify your code in the avatar_uploader we created in the last blog post to :

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# encoding: utf-8

class AvatarUploader < CarrierWave::Uploader::Base
  # include CarrierWaveDirect::Uploader

  # Include RMagick or MiniMagick support:
  include CarrierWave::RMagick
  # include CarrierWave::MiniMagick

  # Include the Sprockets helpers for Rails 3.1+ asset pipeline compatibility:
  include Sprockets::Helpers::RailsHelper
  include Sprockets::Helpers::IsolatedHelper

  # Choose what kind of storage to use for this uploader:
  # storage :file
  storage :fog

  include CarrierWave::MimeTypes
  process :set_content_type

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url
  #   # For Rails 3.1+ asset pipeline compatibility:
  #   # asset_path("fallback/" + [version_name, "default.png"].compact.join('_'))
  #
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  version :thumb do
    process :resize_to_limit => [150, 150]
  end

  version :profile do
    process :resize_to_limit => [350, 350]
  end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  # def extension_white_list
  #   %w(jpg jpeg gif png)
  # end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end

end

That is it. Your photos are now added to your Amazon S3 bucket! Just be careful, you only get so much space on the cloud for free. In the next blog post, I will explain how to increase efficiency with a background task via Sidekiq.

Carrierwave Railscast
Uploading to Amazon S3 Railscast
Sidekiq Railscast

Carrierwave Gem, Part 1

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I have been developing a CMS for students at the Flatiron School. Some gems I used for the first time include Sidekiq, Amazon S3, Carrierwave and Fog. This blog post is a walkthrough of how to implement these gems in your own Rails app. Furthermore, h/t to Ryan Bates of Railscasts for the invaluable information in his videos. This blog post will be broken down into different parts, implementing Carrierwave is the objective of this post.

The first step is to initiate the Carrierwave Gem in order to upload pictures to the app. So, the typical steps:

Add 'carrierwave' to your Gemfile

<div class='bogus-wrapper'><notextile><figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>

$ rails g uploader avatar

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$ rails g migration add_avatar_to_profiles avatar:string

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$ rake db:migrate

Now, our Profile table has an avatar attribute. An uploader folder was also added to your app route directory named after your attribute name, in this case avatar_uploader.rb. Here is the code in the file.

avatar_uploader.rb
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# encoding: utf-8

class AvatarUploader < CarrierWave::Uploader::Base
  # include CarrierWaveDirect::Uploader

  # Include RMagick or MiniMagick support:
  include CarrierWave::RMagick
  # include CarrierWave::MiniMagick

  # Include the Sprockets helpers for Rails 3.1+ asset pipeline compatibility:
  # include Sprockets::Helpers::RailsHelper
  # include Sprockets::Helpers::IsolatedHelper

  # Choose what kind of storage to use for this uploader:
  storage :file
  # storage :fog

  # include CarrierWave::MimeTypes
  # process :set_content_type

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url
  #   # For Rails 3.1+ asset pipeline compatibility:
  #   # asset_path("fallback/" + [version_name, "default.png"].compact.join('_'))
  #
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  version :thumb do
    process :resize_to_limit => [150, 150]
  end

  version :profile do
    process :resize_to_limit => [350, 350]
  end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  # def extension_white_list
  #   %w(jpg jpeg gif png)
  # end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end

end

There is a lot of code in here commented out which will be used in later posts for using both Fog and Amazon S3. I like being able to create different sizes under the version sections, for example

<div class='bogus-wrapper'><notextile><figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>

2 3 4

 version :thumb do
    process :resize_to_limit => [150, 150]
  end


to add elegant versatility to the sizes of your images.

In your Profile model add:

    <div class='bogus-wrapper'><notextile><figure class='code'><figcaption><span>profile.rb </span></figcaption>
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     mount_uploader :avatar, AvatarUploader
      

To display the avatar in your View:

    <div class='bogus-wrapper'><notextile><figure class='code'><figcaption><span>show.html.erb </span></figcaption>
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     <%= image_tag image_url(:thumb) %>
      

In your form:

    <div class='bogus-wrapper'><notextile><figure class='code'><figcaption><span>new.html.erb </span></figcaption>
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     <%= f.file_field :avatar %>
      

That is all, you can now add images of specific sizes to your Rails app!

Carrierwave Railscast
Uploading to Amazon S3 Railscast
Sidekiq Railscast

Binary Search Trees

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Properties

  1. The left subtree of a node contains only nodes with keys less than the node's key.
  2. The right subtree of a node contains only nodes with keys greater than the node's key.
  3. The left and right subtree must each also be a binary search tree.
  4. There must be no duplicate nodes.

Benefits

BST Invariant

For any node x, every key in the left subtree of x is <= x’s key

For any node x, every key in the right subtree of x is >= x’s key


Inorder traversal of a binary search tree visits nodes in sorted order, the left of root (18) are displayed before the right.

Operations

Entry Find (Object k)


How to find smallest key >= k or largest key <= k?

When searching down the tree for a key k that is not in the tree, we encounter both.


<p>Ex. search for 27 as k (from above pic)</p>
<ul>
    <li>Keeps searching nodes to the right, gets to 28 and returns nil</li>
    <li>encounters 25 < k and 28 > k</li>
</ul>

Entry first();
-If empty return null, otherwise start at root and walk down left repeatedly until you reach node with no left child, that node has minimum key.

Entry last();
-Mirror of left, but walks down right tree

Entry insert(Object k, Object v);

The delete operations (where shit gets complex)

Entry remove(Object k);


h/t Jonathan Shewchuk at UC Berkeley

His lecture via Youtube

The Yipit API and Whenever Gem

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Last week Alex and I presented Platt101 at our NYC on Rails Meetup, at the Flatiron School. Platt101 let's a user write reviews about restaurants they have been to and renders those restaurants on a Google Map. The restaurants are based on the 101 best according to New York Magazine. The restaurants a user has been to render in a different color than restaurants a user hasn't had the pleasure of dining. A fellow student (h/t Anthony) suggested we impliment a GroupOn link in our restaurant list in order for a user to provide the user incentive to go dine at given restaurants.

We decided to use the Yipit API in order to aggregate all discount incentives from numerous discount sites such as GroupOn. We accessed the Yipit API via the Yipit gem for Ruby on Rails, created by Gangster. Aside from our client session running a few times, the gem provided for all of our data parsing needs. The Yelp API we used to seed our database with relevant restaurant information included phone numbers. We searched the phone numbers in our database against phone numbers on Yipit in order to find deals for the given restaurants on our list. This functionality is provided with a rake task. Here is the code:


The rake task provides us the ability to use the Whenever gem in order to run the rake task everyday. This way our database in reseeded with new data about restaurant deals on a daily basis. The Whenever gem was easy to impliment.


This code is automatically added to your config > schedule.rb when you run whenever . in terminal. You can customize Whenever to run whenever you want.

Now, this all works well in development, but Platt101 is deployed on Heroku. In production, we needed to reset up the Whenever gem. This is also easy to accomplish on Heroku. Use Heroku Scheduler in order to run a chron job in production. They do make you use input your credit card info, which is whack, but it says free... we shall see.

Platt101 can be found here.

Jambox

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AirPlay

Learning how Airplay works: it allows wireless streaming of audio, video and photos.

My original idea was to rip the music information going onto the Flatiron AirPlay, then automatically tweet this information via Twitter. I liked this idea because we play so much cool and unfamiliar music. It would be great to keep track of what is playing. Over time, I opened a myriad of tabs and discovered many interesting API's. These include a few API's which mirror AirPlay on a laptop (AirParrot. and AirServer.). Also, many music API's were discovered. These include Echonest, Soundcloud and many others.

The original idea went down in flames when I learned how difficult it is to hack the AirPlay. This blog post illustrated how this hacker tried to gain access to the AirPlay from WiFi packets via KisMAC, a derivative of WireShark. Also, there are problems jailbreaking the DRM encryption. The idea is possible, but a crazy task. Idea aborted...

GitHub Play deserves some special recognition. It allows the GitHub offices to wirelessly create playlists synchronously in all of their offices around the globe. The next iteration of our goal was to get the GitHub Play to work locally. You can clone it at the link above. However, GitHub Play relies on an old version of iTunes which includes iTunes DJ. Also, Play ran on Ruby 1.8.7, and the dependencies were a mess. So, our group threw this idea of out the window.

GitHub Play

Our groups next iteration is to simplify the GitHub Play. Currently we are setting up a server where people can upload their mp3's. Directions to create your own streaming music player in Ruby can be found here. The goal of this project is to eventually create a service where a group of people can all upload their songs onto a server and they will be played in sequence on a playlist. For example, if you are at a party, everyone can put songs on a playlist, so that no one person will have complete control of the music. We also want to implement a Reddit-esque leaderboard so people on the server can upvote/downvote songs. If a song gets too many downvotes, it will be erased from the playlist.