SingleForwardable

SingleForwardable也可用于在对象级别设置委派。

printer = String.new
printer.extend SingleForwardable        # prepare object for delegation
printer.def_delegator "STDOUT", "puts"  # add delegation for STDOUT.puts()
printer.puts "Howdy!"

此外，SingleForwardable可用于设置类或模块的委派。

class Implementation
  def self.service
    puts "serviced!"
  end
end

module Facade
  extend SingleForwardable
  def_delegator :Implementation, :service
end

Facade.service #=> serviced!

如果你想同时使用Forwardable和SingleForwardable，你可以使用def_instance_delegator和#def_single_delegator等方法。

公共实例方法

def_delegator(accessor, method, ali = method)

Alias for: def_single_delegator

def_delegators(accessor, *methods)

Alias for: def_single_delegators

def_single_delegator(accessor, method, new_name=method) Show source

定义一个方法，方法委托给该存取器（即它调用同一个名字的方法访问）。如果提供了new_name，它将用作委托方法的名称。

# File lib/forwardable.rb, line 298
def def_single_delegator(accessor, method, ali = method)
  gen = Forwardable._delegator_method(self, accessor, method, ali)

  instance_eval(&gen)
end

Also aliased as: def_delegator

def_single_delegators(accessor, *methods) Show source

用于定义多个委托人方法的快捷方式，但没有规定使用不同的名称。以下两个代码示例具有相同的效果：

def_delegators :@records, :size, :<<, :map

def_delegator :@records, :size
def_delegator :@records, :<<
def_delegator :@records, :map

# File lib/forwardable.rb, line 284
def def_single_delegators(accessor, *methods)
  methods.delete("__send__")
  methods.delete("__id__")
  for method in methods
    def_single_delegator(accessor, method)
  end
end

Also aliased as: def_delegators

delegate(hash)

Alias for: single_delegate

delegate method → accessor Show source

delegate method, method, ... → accessor

以散列为参数。关键是一个符号或一系列符号。这些符号对应于方法名称。该值是该方法将被委派到的访问器。

# File lib/forwardable.rb, line 263
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

Also aliased as: delegate