Module: ActiveRecord::Reflection::ClassMethods

Defined in:
lib/active_record/reflection.rb

Overview

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.

Instance Method Summary collapse

Instance Method Details

#create_reflection(macro, name, options, active_record) ⇒ Object 



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# 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

#reflect_on_aggregation(aggregation) ⇒ Object

Returns the AggregateReflection object for the named aggregation (use the symbol). Example:

Account.reflect_on_aggregation(:balance) # returns the balance AggregateReflection



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# File 'lib/active_record/reflection.rb', line 44

def reflect_on_aggregation(aggregation)
  reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil
end

#reflect_on_all_aggregations ⇒ Object

Returns an array of AggregateReflection objects for all the aggregations in the class.



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# File 'lib/active_record/reflection.rb', line 36

def reflect_on_all_aggregations
  reflections.values.select { |reflection| reflection.is_a?(AggregateReflection) }
end

#reflect_on_all_associations(macro = nil) ⇒ Object

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



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# 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

#reflect_on_association(association) ⇒ Object

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



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# File 'lib/active_record/reflection.rb', line 65

def reflect_on_association(association)
  reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil
end

#reflections ⇒ Object

Returns a hash containing all AssociationReflection objects for the current class Example:

Invoice.reflections
Account.reflections



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# File 'lib/active_record/reflection.rb', line 31

def reflections
  read_inheritable_attribute(:reflections) || write_inheritable_attribute(:reflections, {})
end