method

method_missing

v2.0.3 - Show latest stable - 0 notes - Class: ActiveRecord::Base

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What's this?

method_missing(method_id, *arguments) private

Enables dynamic finders like find_by_user_name(user_name) and find_by_user_name_and_password(user_name, password) that are turned into find(:first, :conditions => ["user_name = ?", user_name]) and find(:first, :conditions => ["user_name = ? AND password = ?", user_name, password]) respectively. Also works for find(:all) by using find_all_by_amount(50) that is turned into find(:all, :conditions => ["amount = ?", 50]).

It’s even possible to use all the additional parameters to find. For example, the full interface for find_all_by_amount is actually find_all_by_amount(amount, options).

This also enables you to initialize a record if it is not found, such as find_or_initialize_by_amount(amount) or find_or_create_by_user_and_password(user, password).

Each dynamic finder or initializer/creator is also defined in the class after it is first invoked, so that future attempts to use it do not run through method_missing.

Show source

# File activerecord/lib/active_record/base.rb, line 1492
        def method_missing(method_id, *arguments)
          if match = /^find_(all_by|by)_([_a-zA-Z]\w*)$/.match(method_id.to_s)
            finder = determine_finder(match)

            attribute_names = extract_attribute_names_from_match(match)
            super unless all_attributes_exists?(attribute_names)

            self.class_eval %{
              def self.#{method_id}(*args)
                options = args.extract_options!
                attributes = construct_attributes_from_arguments([:#{attribute_names.join(',:')}], args)
                finder_options = { :conditions => attributes }
                validate_find_options(options)
                set_readonly_option!(options)

                if options[:conditions]
                  with_scope(:find => finder_options) do
                    ActiveSupport::Deprecation.silence { send(:#{finder}, options) }
                  end
                else
                  ActiveSupport::Deprecation.silence { send(:#{finder}, options.merge(finder_options)) }
                end
              end
            }, __FILE__, __LINE__
            send(method_id, *arguments)
          elsif match = /^find_or_(initialize|create)_by_([_a-zA-Z]\w*)$/.match(method_id.to_s)
            instantiator = determine_instantiator(match)
            attribute_names = extract_attribute_names_from_match(match)
            super unless all_attributes_exists?(attribute_names)

            self.class_eval %{
              def self.#{method_id}(*args)
                if args[0].is_a?(Hash)
                  attributes = args[0].with_indifferent_access
                  find_attributes = attributes.slice(*[:#{attribute_names.join(',:')}])
                else
                  find_attributes = attributes = construct_attributes_from_arguments([:#{attribute_names.join(',:')}], args)
                end

                options = { :conditions => find_attributes }
                set_readonly_option!(options)

                record = find_initial(options)
                if record.nil?
                  record = self.new { |r| r.send(:attributes=, attributes, false) }
                  #{'record.save' if instantiator == :create}
                  record
                else
                  record
                end
              end
            }, __FILE__, __LINE__
            send(method_id, *arguments)
          else
            super
          end
        end

method_missing

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