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Diffstat (limited to 'ruby_1_8_5/lib/forwardable.rb')
| -rw-r--r-- | ruby_1_8_5/lib/forwardable.rb | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/ruby_1_8_5/lib/forwardable.rb b/ruby_1_8_5/lib/forwardable.rb new file mode 100644 index 0000000000..4383ce9bbb --- /dev/null +++ b/ruby_1_8_5/lib/forwardable.rb @@ -0,0 +1,218 @@ +# = forwardable - Support for the Delegation Pattern +# +# $Release Version: 1.1$ +# $Revision: 1.2.2.2 $ +# $Date: 2006/06/02 13:23:01 $ +# by Keiju ISHITSUKA(keiju@ishitsuka.com) +# +# Documentation by James Edward Gray II and Gavin Sinclair +# +# == Introduction +# +# This library allows you delegate method calls to an object, on a method by +# method basis. You can use Forwardable to setup this delegation at the class +# level, or SingleForwardable to handle it at the object level. +# +# == Notes +# +# Be advised, RDoc will not detect delegated methods. +# +# <b>forwardable.rb provides single-method delegation via the +# def_delegator() and def_delegators() methods. For full-class +# delegation via DelegateClass(), see delegate.rb.</b> +# +# == Examples +# +# === Forwardable +# +# Forwardable makes building a new class based on existing work, with a proper +# interface, almost trivial. We want to rely on what has come before obviously, +# but with delegation we can take just the methods we need and even rename them +# as appropriate. In many cases this is preferable to inheritance, which gives +# us the entire old interface, even if much of it isn't needed. +# +# class Queue +# extend Forwardable +# +# def initialize +# @q = [ ] # prepare delegate object +# end +# +# # setup prefered interface, enq() and deq()... +# def_delegator :@q, :push, :enq +# def_delegator :@q, :shift, :deq +# +# # support some general Array methods that fit Queues well +# def_delegators :@q, :clear, :first, :push, :shift, :size +# end +# +# q = Queue.new +# q.enq 1, 2, 3, 4, 5 +# q.push 6 +# +# q.shift # => 1 +# while q.size > 0 +# puts q.deq +# end +# +# q.enq "Ruby", "Perl", "Python" +# puts q.first +# q.clear +# puts q.first +# +# <i>Prints:</i> +# +# 2 +# 3 +# 4 +# 5 +# 6 +# Ruby +# nil +# +# === SingleForwardable +# +# printer = String.new +# printer.extend SingleForwardable # prepare object for delegation +# printer.def_delegator "STDOUT", "puts" # add delegation for STDOUT.puts() +# printer.puts "Howdy!" +# +# <i>Prints:</i> +# +# Howdy! + +# +# 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 <tt>@records</tt>. You could provide the lookup method +# #record_number(), which simply calls #[] on the <tt>@records</tt> +# array, like this: +# +# class RecordCollection +# extend Forwardable +# def_delegator :@records, :[], :record_number +# end +# +# 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 +# end +# +# Also see the example at forwardable.rb. +# +module Forwardable + + @debug = nil + class<<self + # force Forwardable to show up in stack backtraces of delegated methods + attr_accessor :debug + end + + # + # 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. + # + def def_instance_delegators(accessor, *methods) + for method in methods + def_instance_delegator(accessor, method) + end + end + + # + # 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 def_instance_delegator(accessor, method, ali = method) + accessor = accessor.id2name if accessor.kind_of?(Integer) + method = method.id2name if method.kind_of?(Integer) + ali = ali.id2name if ali.kind_of?(Integer) + + module_eval(<<-EOS, "(__FORWARDABLE__)", 1) + def #{ali}(*args, &block) + begin + #{accessor}.__send__(:#{method}, *args, &block) + rescue Exception + $@.delete_if{|s| /^\\(__FORWARDABLE__\\):/ =~ s} unless Forwardable::debug + Kernel::raise + end + end + EOS + end + + alias def_delegators def_instance_delegators + alias def_delegator def_instance_delegator +end + +# +# The SingleForwardable module provides delegation of specified +# methods to a designated object, using the methods #def_delegator +# and #def_delegators. This module is similar to Forwardable, but it works on +# objects themselves, instead of their defining classes. +# +# Also see the example at forwardable.rb. +# +module SingleForwardable + # + # Shortcut for defining multiple delegator methods, but with no + # provision for using a different name. The following two code + # samples have the same effect: + # + # single_forwardable.def_delegators :@records, :size, :<<, :map + # + # single_forwardable.def_delegator :@records, :size + # single_forwardable.def_delegator :@records, :<< + # single_forwardable.def_delegator :@records, :map + # + # See the example at forwardable.rb. + # + def def_singleton_delegators(accessor, *methods) + for method in methods + def_singleton_delegator(accessor, method) + end + end + + # + # 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 example at forwardable.rb. + # + def def_singleton_delegator(accessor, method, ali = method) + accessor = accessor.id2name if accessor.kind_of?(Integer) + method = method.id2name if method.kind_of?(Integer) + ali = ali.id2name if ali.kind_of?(Integer) + + instance_eval(<<-EOS, "(__FORWARDABLE__)", 1) + def #{ali}(*args, &block) + begin + #{accessor}.__send__(:#{method}, *args,&block) + rescue Exception + $@.delete_if{|s| /^\\(__FORWARDABLE__\\):/ =~ s} unless Forwardable::debug + Kernel::raise + end + end + EOS + end + + alias def_delegators def_singleton_delegators + alias def_delegator def_singleton_delegator +end |