Ruby:调用Singleton实例方法的DRY类方法 [英] Ruby: DRY class methods calling Singleton instance methods

问题描述

我有一个Singleton类 ExchangeRegistry ，该类保留所有Exchange对象.

I have the a Singleton class ExchangeRegistry which keeps all the Exchange objects.

无需致电: ExchangeRegistry.instance.exchanges

我希望能够使用: ExchangeRegistry.exchanges

这可行，但是我对重复感到不满意:

This works, but I'm not happy with the repetition:

require 'singleton'

# Ensure an Exchange is only created once
class ExchangeRegistry
  include Singleton

  # Class Methods  ###### Here be duplication and dragons

  def self.exchanges
    instance.exchanges
  end

  def self.get(exchange)
    instance.get(exchange)
  end

  # Instance Methods

  attr_reader :exchanges

  def initialize
    @exchanges = {} # Stores every Exchange created
  end

  def get(exchange)
    @exchanges[Exchange.to_sym exchange] ||= Exchange.create(exchange)
  end
end

我对类方法中的重复不满意.

I'm not happy with the duplication in the class methods.

我已经尝试过使用 Forwardable 和 SimpleDelegator ，但是似乎无法解决这个问题.(其中的大多数示例不是针对类方法，而是针对实例方法)

I've tried using Forwardable and SimpleDelegator but can't seem to get this to DRY out. (Most examples out there are not for class methods but for instance methods)

推荐答案

可转发模块将执行此操作.由于您要转发类方法，因此必须打开eigenclass并在此处定义转发:

The forwardable module will do this. Since you are forwarding class methods, you have to open up the eigenclass and define the forwarding there:

require 'forwardable'
require 'singleton'

class Foo

  include Singleton

  class << self
    extend Forwardable
    def_delegators :instance, :foo, :bar
  end

  def foo
    'foo'
  end

  def bar
    'bar'
  end

end

p Foo.foo    # => "foo"
p Foo.bar    # => "bar"

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