Iacutone.rb

coding and things

Ruby's Fetch Method

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Checking for values in a Rails params hash is complicated. In this post we will use the #fetch method to ensure nil is not called on a params hash.

searches_helper.rb
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  if params[:search][:organization_id].present?
    # do things
  end

The code above will call #present? on nil if params[:search][:organization_id] does not exist.

A better way to write the conditional:

searches_helper.rb
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  if params[:search].present and params[:search][:organization_id].present?
    # do things
  end

Writing a similar conditional with #fetch:

searches_helper.rb
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  if params.fetch(:search, {}).fetch(:organization_id, nil).present?
    # do things
  end

Let’s break this method down into simpler components:

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  params = {}
  puts params.fetch(:search, {})
  // {}

  params[:search] = "searched!"
  puts params.fetch(:search, {})
  // "searched!"

  puts fetch(:organization_id, nil)
  // nil

  params[:organization_id] = 1
  puts params.fetch(:organization_id, nil)
  // 1

I like the ability to call #fetch with a default return value if one does not exist. This leads to better ways to handle nil or catch errors.

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