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Filename : cdesc-Forwardable.ri
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U:RDoc::NormalModule[iI"Forwardable:ET@0o:RDoc::Markup::Document:@parts[o;;[ o:RDoc::Markup::Paragraph;[I"=The Forwardable module provides delegation of specified ;TI"Fmethods to a designated object, using the methods #def_delegator ;TI"and #def_delegators.;To:RDoc::Markup::BlankLine�o;	;[	I">For example, say you have a class RecordCollection which ;TI"Ocontains an array <tt>@records</tt>.  You could provide the lookup method ;TI"G#record_number(), which simply calls #[] on the <tt>@records</tt> ;TI"array, like this:;T@o:RDoc::Markup::Verbatim;[I"require 'forwardable'
;TI"
;TI"class RecordCollection
;TI"  attr_accessor :records
;TI"  extend Forwardable
;TI"4  def_delegator :@records, :[], :record_number
;TI"	end
;T:@format0o;	;[I"*We can use the lookup method like so:;T@o;;[I"r = RecordCollection.new
;TI"r.records = [4,5,6]
;TI" r.record_number(0)  # => 4
;T;0o;	;[I"GFurther, if you wish to provide the methods #size, #<<, and #map, ;TI"Ball of which delegate to @records, this is how you can do it:;T@o;;[I"=class RecordCollection # re-open RecordCollection class
;TI"2  def_delegators :@records, :size, :<<, :map
;TI"	end
;TI"
;TI"r = RecordCollection.new
;TI"r.records = [1,2,3]
;TI"!r.record_number(0)   # => 1
;TI"!r.size               # => 3
;TI",r << 4               # => [1, 2, 3, 4]
;TI",r.map { |x| x * 2 }  # => [2, 4, 6, 8]
;T;0o;	;[I":You can even extend regular objects with Forwardable.;T@o;;[	I"my_hash = Hash.new
;TI"Mmy_hash.extend Forwardable              # prepare object for delegation
;TI"Pmy_hash.def_delegator "STDOUT", "puts"  # add delegation for STDOUT.puts()
;TI"my_hash.puts "Howdy!"
;T;0S:RDoc::Markup::Heading:
leveli:	textI"Another example;T@o;	;[I"UYou could use Forwardable as an alternative to inheritance, when you don't want ;TI"Uto inherit all methods from the superclass. For instance, here is how you might ;TI"Dadd a range of +Array+ instance methods to a new class +Queue+:;T@o;;[!I"class Queue
;TI"  extend Forwardable
;TI"
;TI"  def initialize
;TI"/    @q = [ ]    # prepare delegate object
;TI"  end
;TI"
;TI"7  # setup preferred interface, enq() and deq()...
;TI"&  def_delegator :@q, :push, :enq
;TI"'  def_delegator :@q, :shift, :deq
;TI"
;TI"A  # support some general Array methods that fit Queues well
;TI"@  def_delegators :@q, :clear, :first, :push, :shift, :size
;TI"	end
;TI"
;TI"q = Thread::Queue.new
;TI"q.enq 1, 2, 3, 4, 5
;TI"q.push 6
;TI"
;TI"q.shift    # => 1
;TI"while q.size > 0
;TI"  puts q.deq
;TI"	end
;TI"
;TI"$q.enq "Ruby", "Perl", "Python"
;TI"puts q.first
;TI"
q.clear
;TI"puts q.first
;T;0o;	;[I"This should output:;T@o;;[I"2
;TI"3
;TI"4
;TI"5
;TI"6
;TI"
Ruby
;TI"	nil
;T;0S;
;i;I"
Notes;T@o;	;[I"8Be advised, RDoc will not detect delegated methods.;T@o;	;[I"R+forwardable.rb+ provides single-method delegation via the def_delegator and ;TI"Ndef_delegators methods. For full-class delegation via DelegateClass, see ;TI"+delegate.rb+.;T:
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