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Diffstat (limited to 'ruby_1_8_6/lib/delegate.rb')
| -rw-r--r-- | ruby_1_8_6/lib/delegate.rb | 335 |
1 files changed, 335 insertions, 0 deletions
diff --git a/ruby_1_8_6/lib/delegate.rb b/ruby_1_8_6/lib/delegate.rb new file mode 100644 index 0000000000..d810ccad42 --- /dev/null +++ b/ruby_1_8_6/lib/delegate.rb @@ -0,0 +1,335 @@ +# = 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 +# @_sd_obj = obj # store obj for future use +# end +# +# def __getobj__ +# @_sd_obj # return object we are delegating to, required +# end +# +# def __setobj__(obj) +# @_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 + + # + # Pass in the _obj_ to delegate method calls to. All methods supported by + # _obj_ will be delegated to. + # + def initialize(obj) + preserved = ::Kernel.public_instance_methods(false) + preserved -= ["to_s","to_a","inspect","==","=~","==="] + for t in self.class.ancestors + preserved |= t.public_instance_methods(false) + preserved |= t.private_instance_methods(false) + preserved |= t.protected_instance_methods(false) + break if t == Delegator + end + preserved << "singleton_method_added" + for method in obj.methods + next if preserved.include? method + begin + eval <<-EOS + def self.#{method}(*args, &block) + begin + __getobj__.__send__(:#{method}, *args, &block) + rescue Exception + $@.delete_if{|s| /:in `__getobj__'$/ =~ s} #` + $@.delete_if{|s| /^\\(eval\\):/ =~ s} + Kernel::raise + end + end + EOS + rescue SyntaxError + raise NameError, "invalid identifier %s" % method, caller(4) + end + end + end + alias initialize_methods initialize + + # Handles the magic of delegation through \_\_getobj\_\_. + def method_missing(m, *args) + target = self.__getobj__ + unless target.respond_to?(m) + super(m, *args) + end + target.__send__(m, *args) + end + + # + # Checks for a method provided by this the delegate object by fowarding the + # call through \_\_getobj\_\_. + # + def respond_to?(m) + return true if super + return self.__getobj__.respond_to?(m) + 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 + + # Serialization support for the object returned by \_\_getobj\_\_. + def marshal_dump + __getobj__ + end + # Reinitializes delegation from a serialized object. + def marshal_load(obj) + initialize_methods(obj) + __setobj__(obj) + end +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 + + # Pass in the _obj_ you would like to delegate method calls to. + def initialize(obj) + super + @_sd_obj = obj + end + + # Returns the current object method calls are being delegated to. + def __getobj__ + @_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) + @_sd_obj = obj + end + + # Clone support for the object returned by \_\_getobj\_\_. + def clone + super + __setobj__(__getobj__.clone) + end + # Duplication support for the object returned by \_\_getobj\_\_. + def dup(obj) + super + __setobj__(__getobj__.dup) + end +end + +# :stopdoc: +# backward compatibility ^_^;;; +Delegater = Delegator +SimpleDelegater = SimpleDelegator +# :startdoc: + +# +# The primary interface to this library. Use to setup delegation when defining +# your class. +# +# class MyClass < DelegateClass( ClassToDelegateTo ) # Step 1 +# def initiaize +# super(obj_of_ClassToDelegateTo) # Step 2 +# end +# end +# +def DelegateClass(superclass) + klass = Class.new + methods = superclass.public_instance_methods(true) + methods -= ::Kernel.public_instance_methods(false) + methods |= ["to_s","to_a","inspect","==","=~","==="] + klass.module_eval { + def initialize(obj) # :nodoc: + @_dc_obj = obj + end + def method_missing(m, *args) # :nodoc: + unless @_dc_obj.respond_to?(m) + super(m, *args) + end + @_dc_obj.__send__(m, *args) + end + def respond_to?(m) # :nodoc: + return true if super + return @_dc_obj.respond_to?(m) + end + def __getobj__ # :nodoc: + @_dc_obj + end + def __setobj__(obj) # :nodoc: + raise ArgumentError, "cannot delegate to self" if self.equal?(obj) + @_dc_obj = obj + end + def clone # :nodoc: + super + __setobj__(__getobj__.clone) + end + def dup # :nodoc: + super + __setobj__(__getobj__.dup) + end + } + for method in methods + begin + klass.module_eval <<-EOS + def #{method}(*args, &block) + begin + @_dc_obj.__send__(:#{method}, *args, &block) + rescue + $@[0,2] = nil + raise + end + end + EOS + rescue SyntaxError + raise NameError, "invalid identifier %s" % method, caller(3) + 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 + + foo = Object.new + def foo.test + 25 + end + def foo.error + raise 'this is OK' + end + foo2 = SimpleDelegator.new(foo) + p foo.test == foo2.test # => true + foo2.error # raise error! +end |