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# Delegation class that delegates even methods defined in super class,
# which can not be covered with normal method_missing hack.
#
# Delegator is the abstract delegation class. Need to redefine
# `__getobj__' method in the subclass. SimpleDelegator is the
# concrete subclass for simple delegation.
#
# Usage:
# foo = Object.new
# foo2 = SimpleDelegator.new(foo)
# foo.hash == foo2.hash # => false
#
# Foo = DelegateClass(Array)
#
# class ExtArray<DelegateClass(Array)
# ...
# end
class Delegator
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
def __getobj__
raise NotImplementedError, "need to define `__getobj__'"
end
def marshal_dump
__getobj__
end
def marshal_load(obj)
initialize_methods(obj)
end
end
class SimpleDelegator<Delegator
def initialize(obj)
super
@_sd_obj = obj
end
def __getobj__
@_sd_obj
end
def __setobj__(obj)
raise ArgumentError, "cannot delegate to self" if self.equal?(obj)
@_sd_obj = obj
end
def clone
super
__setobj__(__getobj__.clone)
end
def dup
super
__setobj__(__getobj__.dup)
end
end
# backward compatibility ^_^;;;
Delegater = Delegator
SimpleDelegater = SimpleDelegator
#
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)
@_dc_obj = obj
end
def method_missing(m, *args)
unless @_dc_obj.respond_to?(m)
super(m, *args)
end
@_dc_obj.__send__(m, *args)
end
def __getobj__
@_dc_obj
end
def __setobj__(obj)
raise ArgumentError, "cannot delegate to self" if self.equal?(obj)
@_dc_obj = obj
end
def clone
super
__setobj__(__getobj__.clone)
end
def dup
super
__setobj__(__getobj__.dup)
end
}
for method in methods
begin
klass.module_eval <<-EOS, __FILE__, __LINE__+1
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
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
|
