Forwardable

module Forwardable

可转换模块使用方法def_delegator和def_delegators将指定方法委托给指定的对象。

例如，假设你有一个RecordCollection类，它包含一个数组@records。您可以提供查找方法record_number()，该方法只需在@records数组中调用[] ，如下所示：

require 'forwardable'

class RecordCollection
  attr_accessor :records
  extend Forwardable
  def_delegator :@records, :[], :record_number
end

我们可以像这样使用查找方法：

r = RecordCollection.new
r.records = [4,5,6]
r.record_number(0)  # => 4

此外，如果您希望提供方法大小，<

class RecordCollection # re-open RecordCollection class
  def_delegators :@records, :size, :<<, :map
end

r = RecordCollection.new
r.records = [1,2,3]
r.record_number(0)   # => 1
r.size               # => 3
r << 4               # => [1, 2, 3, 4]
r.map { |x| x * 2 }  # => [2, 4, 6, 8]

您甚至可以使用Forwardable扩展常规对象。

my_hash = Hash.new
my_hash.extend Forwardable              # prepare object for delegation
my_hash.def_delegator "STDOUT", "puts"  # add delegation for STDOUT.puts()
my_hash.puts "Howdy!"

另一个例子

我们希望依靠之前明显发生的事情，但通过授权，我们可以只采用我们需要的方法，甚至适当地重命名它们。在许多情况下，这比继承更可取，这使我们可以使用完整的旧界面，即使其中大部分都不需要。

class Queue
  extend Forwardable

  def initialize
    @q = [ ]    # prepare delegate object
  end

  # setup preferred interface, enq() and deq()...
  def_delegator :@q, :push, :enq
  def_delegator :@q, :shift, :deq

  # support some general Array methods that fit Queues well
  def_delegators :@q, :clear, :first, :push, :shift, :size
end

q = Queue.new
q.enq 1, 2, 3, 4, 5
q.push 6

q.shift    # => 1
while q.size > 0
  puts q.deq
end

q.enq "Ruby", "Perl", "Python"
puts q.first
q.clear
puts q.first

这应该输出：

2
3
4
5
6
Ruby
nil

注意

请注意，RDoc不会检测委托方法。

forwardable.rb通过#def_delegator和#def_delegators方法提供单方法委托。对于通过DelegateClass的full-class授权，请参阅delegate.rb。

常量

FORWARDABLE_VERSION

forwardable.rb版本

属性

debugRW

ignored

Public Instance Methods

def_delegator(accessor, method, ali = method)

Alias for: def_instance_delegator

def_delegators(accessor, *methods)

Alias for: def_instance_delegators

def_instance_delegator(accessor, method, ali = method) Show source

使用可选的别名名称定义method为委托人实例方法ali。方法调用ali将被委托给accessor.method。

class MyQueue
  extend Forwardable
  attr_reader :queue
  def initialize
    @queue = []
  end

  def_delegator :@queue, :push, :mypush
end

q = MyQueue.new
q.mypush 42
q.queue    #=> [42]
q.push 23  #=> NoMethodError

# File lib/forwardable.rb, line 179
def def_instance_delegator(accessor, method, ali = method)
  gen = Forwardable._delegator_method(self, accessor, method, ali)

  # If it's not a class or module, it's an instance
  (Module === self ? self : singleton_class).module_eval(&gen)
end

Also aliased as: def_delegator

def_instance_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 152
def def_instance_delegators(accessor, *methods)
  methods.delete("__send__")
  methods.delete("__id__")
  for method in methods
    def_instance_delegator(accessor, method)
  end
end

Also aliased as: def_delegators

delegate(hash)

Alias for: instance_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 131
def instance_delegate(hash)
  hash.each do |methods, accessor|
    unless defined?(methods.each)
      def_instance_delegator(accessor, methods)
    else
      methods.each {|method| def_instance_delegator(accessor, method)}
    end
  end
end

Also aliased as: delegate