Module: ActiveRecord::Reflection::ClassMethods

### Home Classes Methods

### In Files

- lib/active_record/reflection.rb

### Methods

- #create_reflection
- #reflect_on_aggregation
- #reflect_on_all_aggregations
- #reflect_on_all_associations
- #reflect_on_all_autosave_associations
- #reflect_on_association
- #reflections

### Files

- README.rdoc

### Class/Module Index

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# ActiveRecord::Reflection::ClassMethods

Reflection enables to interrogate Active Record classes and objects about their associations and aggregations. This information can, for example, 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.

### Public Instance Methods

create_reflection(macro, name, options, active_record) click to toggle source

    # File lib/active_record/reflection.rb, line 15
    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) click to toggle source

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

    Account.reflect_on_aggregation(:balance) # => the balance AggregateReflection

    # File lib/active_record/reflection.rb, line 46
    def reflect_on_aggregation(aggregation)
      reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil
    end

reflect_on_all_aggregations() click to toggle source

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

    # File lib/active_record/reflection.rb, line 38
    def reflect_on_all_aggregations
      reflections.values.select { |reflection| reflection.is_a?(AggregateReflection) }
    end

reflect_on_all_associations(macro = nil) click to toggle source

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 lib/active_record/reflection.rb, line 60
    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_all_autosave_associations() click to toggle source

Returns an array of AssociationReflection objects for all associations which have `:autosave` enabled.

    # File lib/active_record/reflection.rb, line 75
    def reflect_on_all_autosave_associations
      reflections.values.select { |reflection| reflection.options[:autosave] }
    end

reflect_on_association(association) click to toggle source

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 lib/active_record/reflection.rb, line 70
    def reflect_on_association(association)
      reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil
    end

reflections() click to toggle source

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

    Invoice.reflections
    Account.reflections

    # File lib/active_record/reflection.rb, line 33
    def reflections
      read_inheritable_attribute(:reflections) || write_inheritable_attribute(:reflections, {})
    end

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