Ruby Decorator_Kotiya Sanae的早苗神社

module Kernel
	def at(a)
			cc = a.shift.new(*a)
			self.class_eval {
				org = method(:method_added)
				send :define_singleton_method,:method_added, &lambda{|sym, *args|
					return org.call(sym, *args)  if (sym==:method_added)
					send(:define_singleton_method,:method_added, &org)
					x = instance_method(sym)
					send(:define_method, sym,  &cc.call(sym, x))
				}
			}
	end
	
	class Author
		def initialize(name)
			@name = name
		end
		def call(sym, block)
			name = @name
			lambda {|*args|
				puts "Author #{name}\nFunction #{sym}"
				block.bind(instance_eval{self}).call(*args)
			}	
		end
	end

	class Rev
		def initialize(rev)
			@rev = rev
		end
		def call(sym, block)
			rev = @rev
			lambda {|*args|
				puts "Revision: #{rev}"
				block.call(*args)
			}	
		end
	end

	at [Rev, 5]
	def print_hello
		puts "Hello world"
	end

	at [Author, "pochy"]
	def ok
			puts "ok"
	end

	print_hello
	ok
	ok
end

class Check
	def initialize(*args)
		@x = *args
	end
	def call(sym, block)
		x = @x
		lambda{|*args|
			raise "Wrong number of arguments (#{args.length} of #{x.length}"  if args.length != x.length
			x.each_index{|i|
				raise "Type error #{args[i].class} for #{x[i]}" unless args[i].class==x[i]
			}
			block.bind(instance_eval{self}).call(*args)
		}
	end
end

class A
	
	at [Check, Fixnum, Fixnum]
	def add(a,b)
		a+b
	end
	
end

puts A.new.add(3,4,5)module Kernel
	def at(a)
			cc = a.shift.new(*a