Question

I am using Ruby on Rails 3.0.7 and I would like to know how to initialize\build “custom” data structures responding to the where method as like it works, for example, for common RoR AssociationCollection objects.

For example:

# The following code should work after build the 'test_data' as well... 
# but how to build that?

test_data.where(:test_attribute => 'test_value')

Answer 1

I’m not entirely clear on what you’re after, but you could create a wrapper around (for example) an array of hashes that used where to do searching.

class Search
  def initialize(data)
    @data = data
  end

  def where(filters={})
    @data.select do |item|
      filters.all?{|key, value| item[key] == value }
    end
  end
end



data = [
  { :name => 'Sam', :age => 27, :gender => 'M' },
  { :name => 'Sue', :age => 27, :gender => 'F' },
  { :name => 'Bob', :age => 32, :gender => 'M' }
]

search = Search.new(data)
search.where(:age => 27)      # returns array containing Sam and Sue hashes
search.where(:gender => 'M')  # returns array containing Sam and Bob hashes
search.where(:age => 27, :gender => 'M')  # returns array containing just Sam