SingleForwardable
can be used to setup delegation at the object level as well.
printer = String.new printer.extend SingleForwardable # prepare object for delegation printer.def_delegator "STDOUT", "puts" # add delegation for STDOUT.puts() printer.puts "Howdy!"
Also, SingleForwardable
can be used to set up delegation for a Class or Module.
class Implementation def self.service puts "serviced!" end end module Facade extend SingleForwardable def_delegator :Implementation, :service end Facade.service #=> serviced!
If you want to use both Forwardable and SingleForwardable
, you can use methods def_instance_delegator and def_single_delegator
, etc.
Defines a method method which delegates to accessor (i.e. it calls the method of the same name in accessor). If new_name is provided, it is used as the name for the delegate method. Returns the name of the method defined.
# File forwardable.rb, line 308 def def_single_delegator(accessor, method, ali = method) gen = Forwardable._delegator_method(self, accessor, method, ali) ret = instance_eval(&gen) singleton_class.__send__(:ruby2_keywords, ali) if RUBY_VERSION >= '2.7' ret end
Shortcut for defining multiple delegator methods, but with no provision for using a different name. The following two code samples have the same effect:
def_delegators :@records, :size, :<<, :map def_delegator :@records, :size def_delegator :@records, :<< def_delegator :@records, :map
# File forwardable.rb, line 294 def def_single_delegators(accessor, *methods) methods.each do |method| next if /\A__(?:send|id)__\z/ =~ method def_single_delegator(accessor, method) end end
Takes a hash as its argument. The key is a symbol or an array of symbols. These symbols correspond to method names. The value is the accessor to which the methods will be delegated.
# File forwardable.rb, line 273 def single_delegate(hash) hash.each do |methods, accessor| unless defined?(methods.each) def_single_delegator(accessor, methods) else methods.each {|method| def_single_delegator(accessor, method)} end end end