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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
preserved = ["__id__", "object_id", "__send__", "respond_to?"]
instance_methods.each do |m|
next if preserved.include?(m)
undef_method m
end
def initialize(obj)
__setobj__(obj)
end
def method_missing(m, *args)
begin
target = self.__getobj__
unless target.respond_to?(m)
super(m, *args)
end
target.__send__(m, *args)
rescue Exception
$@.delete_if{|s| /^#{__FILE__}:\d+:in `method_missing'$/ =~ s} #`
::Kernel::raise
end
end
def respond_to?(m)
return true if super
return self.__getobj__.respond_to?(m)
end
def __getobj__
raise NotImplementedError, "need to define `__getobj__'"
end
def __setobj__(obj)
raise NotImplementedError, "need to define `__setobj__'"
end
def marshal_dump
__getobj__
end
def marshal_load(obj)
__setobj__(obj)
end
end
class SimpleDelegator<Delegator
def __getobj__
@_sd_obj
end
def __setobj__(obj)
raise ArgumentError, "cannot delegate to self" if self.equal?(obj)
@_sd_obj = obj
end
def clone
copy = super
copy.__setobj__(__getobj__.clone)
copy
end
def dup
copy = super
copy.__setobj__(__getobj__.dup)
copy
end
end
# backward compatibility ^_^;;;
Delegater = Delegator
SimpleDelegater = SimpleDelegator
#
def DelegateClass(superclass)
klass = Class.new
methods = superclass.public_instance_methods(true)
methods -= [
"__id__", "object_id", "__send__", "respond_to?",
"initialize", "method_missing", "__getobj__", "__setobj__",
"clone", "dup", "marshal_dump", "marshal_load",
]
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 respond_to?(m)
return true if super
return @_dc_obj.respond_to?(m)
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
|
