Reflection allows you to interrogate Active Record classes and objects about their associations and aggregations. This information can, for example, be used in a form builder that took an Active Record object and created input fields for all of the attributes depending on their type and displayed the associations to other objects.
You can find the interface for the AggregateReflection and AssociationReflection classes in the abstract MacroReflection class.
# File lib/active_record/reflection.rb, line 13 def create_reflection(macro, name, options, active_record) case macro when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many klass = options[:through] ? ThroughReflection : AssociationReflection reflection = klass.new(macro, name, options, active_record) when :composed_of reflection = AggregateReflection.new(macro, name, options, active_record) end write_inheritable_hash :reflections, name => reflection reflection end
Returns the AggregateReflection object for the named aggregation (use the symbol). Example:
Account.reflect_on_aggregation(:balance) # returns the balance AggregateReflection
# File lib/active_record/reflection.rb, line 44 def reflect_on_aggregation(aggregation) reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil end
Returns an array of AggregateReflection objects for all the aggregations in the class.
# File lib/active_record/reflection.rb, line 36 def reflect_on_all_aggregations reflections.values.select { |reflection| reflection.is_a?(AggregateReflection) } end
Returns an array of AssociationReflection objects for all the associations in the class. If you only want to reflect on a certain association type, pass in the symbol (:has_many, :has_one, :belongs_to) for that as the first parameter. Example:
Account.reflect_on_all_associations # returns an array of all associations Account.reflect_on_all_associations(:has_many) # returns an array of all has_many associations
# File lib/active_record/reflection.rb, line 55 def reflect_on_all_associations(macro = nil) association_reflections = reflections.values.select { |reflection| reflection.is_a?(AssociationReflection) } macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections end
Returns an array of AssociationReflection objects for all associations which have :autosave enabled.
# File lib/active_record/reflection.rb, line 70 def reflect_on_all_autosave_associations reflections.values.select { |reflection| reflection.options[:autosave] } end
Returns the AssociationReflection object for the named association (use the symbol). Example:
Account.reflect_on_association(:owner) # returns the owner AssociationReflection Invoice.reflect_on_association(:line_items).macro # returns :has_many
# File lib/active_record/reflection.rb, line 65 def reflect_on_association(association) reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil end
Returns a hash containing all AssociationReflection objects for the current class Example:
Invoice.reflections Account.reflections
# File lib/active_record/reflection.rb, line 31 def reflections read_inheritable_attribute(:reflections) || write_inheritable_attribute(:reflections, {}) end
Generated with the Darkfish Rdoc Generator 2.