Reflection enables the ability to examine the associations and aggregations of Active Record classes and objects. This information, for example, can be used in a form builder that takes an Active Record object and creates input fields for all of the attributes depending on their type and displays the associations to other objects.
MacroReflection
class has info for AggregateReflection and AssociationReflection classes.
# File activerecord/lib/active_record/reflection.rb, line 67 def reflect_on_aggregation(aggregation) aggregate_reflections[aggregation.to_s] end
Returns the AggregateReflection object for the named aggregation
(use the symbol).
Account.reflect_on_aggregation(:balance) # => the balance AggregateReflection
# File activerecord/lib/active_record/reflection.rb, line 59 def reflect_on_all_aggregations aggregate_reflections.values end
Returns an array of AggregateReflection objects for all the aggregations in the class.
# File activerecord/lib/active_record/reflection.rb, line 104 def reflect_on_all_associations(macro = nil) association_reflections = reflections.values association_reflections.select! { |reflection| reflection.macro == macro } if macro association_reflections 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
) 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 activerecord/lib/active_record/reflection.rb, line 124 def reflect_on_all_autosave_associations reflections.values.select { |reflection| reflection.options[:autosave] } end
Returns an array of AssociationReflection objects for all associations which have :autosave
enabled.
# File activerecord/lib/active_record/reflection.rb, line 115 def reflect_on_association(association) reflections[association.to_s] end
Returns the AssociationReflection object for the association
(use the symbol).
Account.reflect_on_association(:owner) # returns the owner AssociationReflection Invoice.reflect_on_association(:line_items).macro # returns :has_many
# File activerecord/lib/active_record/reflection.rb, line 75 def reflections @__reflections ||= begin ref = {} _reflections.each do |name, reflection| parent_reflection = reflection.parent_reflection if parent_reflection parent_name = parent_reflection.name ref[parent_name.to_s] = parent_reflection else ref[name] = reflection end end ref end end
Returns a Hash
of name of the reflection as the key and an AssociationReflection as the value.
Account.reflections # => {"balance" => AggregateReflection}
© 2004–2021 David Heinemeier Hansson
Licensed under the MIT License.