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.
# File tmp/rubies/ruby-2.7.6/lib/forwardable.rb, line 305
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
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 tmp/rubies/ruby-2.7.6/lib/forwardable.rb, line 291
def def_single_delegators(accessor, *methods)
methods.each do |method|
next if /\A__(?:send|id)__\z/ =~ method
def_single_delegator(accessor, method)
end
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 tmp/rubies/ruby-2.7.6/lib/forwardable.rb, line 270
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
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.