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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 # => true
#
# Foo = DelegateClass(Array)
#
# class ExtArray<DelegateClass(Array)
# ...
# end
class Delegator
def initialize(obj)
preserved = ::Kernel.instance_methods
for t in self.type.ancestors
preserved |= t.instance_methods
break if t == Delegator
end
preserved -= ["to_s","to_a","inspect","hash","eql?","==","=~","==="]
for method in obj.methods
next if preserved.include? method
eval <<EOS
def self.#{method}(*args, &block)
begin
__getobj__.__send__(:#{method}, *args, &block)
rescue Exception
n = if /:in `__getobj__'$/ =~ $@[0] then 1 else 2 end #`
$@[1,n] = nil
raise
end
end
EOS
end
end
def __getobj__
raise NotImplementError, "need to define `__getobj__'"
end
end
class SimpleDelegator<Delegator
def initialize(obj)
super
@obj = obj
end
def __getobj__
@obj
end
def __setobj__(obj)
@obj = obj
end
end
# backward compatibility ^_^;;;
Delegater = Delegator
SimpleDelegater = SimpleDelegator
#
def DelegateClass(superclass)
klass = Class.new
methods = superclass.instance_methods
methods -= ::Kernel.instance_methods
methods |= ["to_s","to_a","inspect","hash","eql?","==","=~","==="]
klass.module_eval <<EOS
def initialize(obj)
@obj = obj
end
EOS
for method in methods
klass.module_eval <<EOS
def #{method}(*args, &block)
begin
@obj.__send__(:#{method}, *args, &block)
rescue
$@[0,2] = nil
raise
end
end
EOS
end
return klass;
end
if __FILE__ == $0
class ExtArray<DelegateClass(Array)
def initialize()
super([])
end
end
ary = ExtArray.new
p ary.type
ary.push 25
p ary
foo = Object.new
def foo.test
raise 'this is OK'
end
foo2 = SimpleDelegator.new(foo)
p foo.hash == foo2.hash # => true
foo.test # raise error!
end
|
