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Diffstat (limited to 'trunk/lib/delegate.rb')
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diff --git a/trunk/lib/delegate.rb b/trunk/lib/delegate.rb deleted file mode 100644 index 629753fe3a..0000000000 --- a/trunk/lib/delegate.rb +++ /dev/null @@ -1,331 +0,0 @@ -# = delegate -- Support for the Delegation Pattern -# -# Documentation by James Edward Gray II and Gavin Sinclair -# -# == Introduction -# -# This library provides three different ways to delegate method calls to an -# object. The easiest to use is SimpleDelegator. Pass an object to the -# constructor and all methods supported by the object will be delegated. This -# object can be changed later. -# -# Going a step further, the top level DelegateClass method allows you to easily -# setup delegation through class inheritance. This is considerably more -# flexible and thus probably the most common use for this library. -# -# Finally, if you need full control over the delegation scheme, you can inherit -# from the abstract class Delegator and customize as needed. (If you find -# yourself needing this control, have a look at _forwardable_, also in the -# standard library. It may suit your needs better.) -# -# == Notes -# -# Be advised, RDoc will not detect delegated methods. -# -# <b>delegate.rb provides full-class delegation via the -# DelegateClass() method. For single-method delegation via -# def_delegator(), see forwardable.rb.</b> -# -# == Examples -# -# === SimpleDelegator -# -# Here's a simple example that takes advantage of the fact that -# SimpleDelegator's delegation object can be changed at any time. -# -# class Stats -# def initialize -# @source = SimpleDelegator.new([]) -# end -# -# def stats( records ) -# @source.__setobj__(records) -# -# "Elements: #{@source.size}\n" + -# " Non-Nil: #{@source.compact.size}\n" + -# " Unique: #{@source.uniq.size}\n" -# end -# end -# -# s = Stats.new -# puts s.stats(%w{James Edward Gray II}) -# puts -# puts s.stats([1, 2, 3, nil, 4, 5, 1, 2]) -# -# <i>Prints:</i> -# -# Elements: 4 -# Non-Nil: 4 -# Unique: 4 -# -# Elements: 8 -# Non-Nil: 7 -# Unique: 6 -# -# === DelegateClass() -# -# Here's a sample of use from <i>tempfile.rb</i>. -# -# A _Tempfile_ object is really just a _File_ object with a few special rules -# about storage location and/or when the File should be deleted. That makes for -# an almost textbook perfect example of how to use delegation. -# -# class Tempfile < DelegateClass(File) -# # constant and class member data initialization... -# -# def initialize(basename, tmpdir=Dir::tmpdir) -# # build up file path/name in var tmpname... -# -# @tmpfile = File.open(tmpname, File::RDWR|File::CREAT|File::EXCL, 0600) -# -# # ... -# -# super(@tmpfile) -# -# # below this point, all methods of File are supported... -# end -# -# # ... -# end -# -# === Delegator -# -# SimpleDelegator's implementation serves as a nice example here. -# -# class SimpleDelegator < Delegator -# def initialize(obj) -# super # pass obj to Delegator constructor, required -# @delegate_sd_obj = obj # store obj for future use -# end -# -# def __getobj__ -# @delegate_sd_obj # return object we are delegating to, required -# end -# -# def __setobj__(obj) -# @delegate_sd_obj = obj # change delegation object, a feature we're providing -# end -# -# # ... -# end - -# -# Delegator is an abstract class used to build delegator pattern objects from -# subclasses. Subclasses should redefine \_\_getobj\_\_. For a concrete -# implementation, see SimpleDelegator. -# -class Delegator - preserved = [ - :__id__, :object_id, :__send__, :public_send, :respond_to?, :send, - :instance_eval, :instance_exec, :extend, - ] - instance_methods.each do |m| - next if preserved.include?(m) - undef_method m - end - - module MethodDelegation - # - # Pass in the _obj_ to delegate method calls to. All methods supported by - # _obj_ will be delegated to. - # - def initialize(obj) - __setobj__(obj) - end - - # Handles the magic of delegation through \_\_getobj\_\_. - def method_missing(m, *args, &block) - begin - target = self.__getobj__ - unless target.respond_to?(m) - super(m, *args, &block) - else - target.__send__(m, *args, &block) - end - rescue Exception - $@.delete_if{|s| %r"\A#{__FILE__}:\d+:in `method_missing'\z"o =~ s} - ::Kernel::raise - end - end - - # - # Checks for a method provided by this the delegate object by fowarding the - # call through \_\_getobj\_\_. - # - def respond_to?(m, include_private = false) - return true if super - return self.__getobj__.respond_to?(m, include_private) - end - - # - # Returns true if two objects are considered same. - # - def ==(obj) - return true if obj.equal?(self) - self.__getobj__ == obj - end - - # - # Returns true only if two objects are identical. - # - def equal?(obj) - self.object_id == obj.object_id - end - - # - # This method must be overridden by subclasses and should return the object - # method calls are being delegated to. - # - def __getobj__ - raise NotImplementedError, "need to define `__getobj__'" - end - - # - # This method must be overridden by subclasses and change the object delegate - # to _obj_. - # - def __setobj__(obj) - raise NotImplementedError, "need to define `__setobj__'" - end - - # Serialization support for the object returned by \_\_getobj\_\_. - def marshal_dump - __getobj__ - end - # Reinitializes delegation from a serialized object. - def marshal_load(obj) - __setobj__(obj) - end - - # Clone support for the object returned by \_\_getobj\_\_. - def clone - new = super - new.__setobj__(__getobj__.clone) - new - end - # Duplication support for the object returned by \_\_getobj\_\_. - def dup - new = super - new.__setobj__(__getobj__.dup) - new - end - end - include MethodDelegation -end - -# -# A concrete implementation of Delegator, this class provides the means to -# delegate all supported method calls to the object passed into the constructor -# and even to change the object being delegated to at a later time with -# \_\_setobj\_\_ . -# -class SimpleDelegator<Delegator - # Returns the current object method calls are being delegated to. - def __getobj__ - @delegate_sd_obj - end - - # - # Changes the delegate object to _obj_. - # - # It's important to note that this does *not* cause SimpleDelegator's methods - # to change. Because of this, you probably only want to change delegation - # to objects of the same type as the original delegate. - # - # Here's an example of changing the delegation object. - # - # names = SimpleDelegator.new(%w{James Edward Gray II}) - # puts names[1] # => Edward - # names.__setobj__(%w{Gavin Sinclair}) - # puts names[1] # => Sinclair - # - def __setobj__(obj) - raise ArgumentError, "cannot delegate to self" if self.equal?(obj) - @delegate_sd_obj = obj - end -end - -# :stopdoc: -def Delegator.delegating_block(mid) - lambda do |*args, &block| - begin - @delegate_dc_obj.__send__(mid, *args, &block) - rescue - re = /\A#{Regexp.quote(__FILE__)}:#{__LINE__-2}:/o - $!.backtrace.delete_if {|t| re =~ t} - raise - end - end -end -# :startdoc: - -# -# The primary interface to this library. Use to setup delegation when defining -# your class. -# -# class MyClass < DelegateClass( ClassToDelegateTo ) # Step 1 -# def initialize -# super(obj_of_ClassToDelegateTo) # Step 2 -# end -# end -# -def DelegateClass(superclass) - klass = Class.new - methods = superclass.public_instance_methods(true) - methods -= [ - :__id__, :object_id, :__send__, :public_send, :respond_to?, :send, - :==, :equal?, :initialize, :method_missing, :__getobj__, :__setobj__, - :clone, :dup, :marshal_dump, :marshal_load, :instance_eval, :instance_exec, - :extend, - ] - klass.module_eval { - include Delegator::MethodDelegation - def __getobj__ # :nodoc: - @delegate_dc_obj - end - def __setobj__(obj) # :nodoc: - raise ArgumentError, "cannot delegate to self" if self.equal?(obj) - @delegate_dc_obj = obj - end - } - klass.module_eval do - methods.each do |method| - define_method(method, Delegator.delegating_block(method)) - end - end - return klass -end - -# :enddoc: - -if __FILE__ == $0 - class ExtArray<DelegateClass(Array) - def initialize() - super([]) - end - end - - ary = ExtArray.new - p ary.class - ary.push 25 - p ary - ary.push 42 - ary.each {|x| p x} - - foo = Object.new - def foo.test - 25 - end - def foo.iter - yield self - end - def foo.error - raise 'this is OK' - end - foo2 = SimpleDelegator.new(foo) - p foo2 - foo2.instance_eval{print "foo\n"} - p foo.test == foo2.test # => true - p foo2.iter{[55,true]} # => true - foo2.error # raise error! -end |