The Forwardable module provides delegation of specified methods to a designated object, using the methods def_delegator and def_delegators.

For example, say you have a class RecordCollection which contains an array @records. You could provide the lookup method record_number(), which simply calls #[] on the @records array, like this:

  class RecordCollection
    extend Forwardable
    def_delegator :@records, :[], :record_number

Further, if you wish to provide the methods size, #<<, and map, all of which delegate to @records, this is how you can do it:

  class RecordCollection
    # extend Forwardable, but we did that above
    def_delegators :@records, :size, :<<, :map

Also see the example at forwardable.rb.


Name Visibility R/W Description
debug public RW force Forwardable to show up in stack backtraces of delegated methods



Visibility Signature
public def_delegator (accessor, method, ali = method)
public def_delegators (accessor, *methods)
public def_instance_delegator (accessor, method, ali = method)
public def_instance_delegators (accessor, *methods)

Instance Method Detail

def_delegator(accessor, method, ali = method)

def_delegators(accessor, *methods)

def_instance_delegator(accessor, method, ali = method)

Defines a method method which delegates to obj (i.e. it calls the method of the same name in obj). If new_name is provided, it is used as the name for the delegate method.

See the examples at Forwardable and forwardable.rb.

def_instance_delegators(accessor, *methods)

Shortcut for defining multiple delegator methods, but with no provision for using a different name. The following two code samples have the same effect:

  def_delegators :@records, :size, :<<, :map

  def_delegator :@records, :size
  def_delegator :@records, :<<
  def_delegator :@records, :map

See the examples at Forwardable and forwardable.rb.