在普通 Ruby class 中使用方法回调

Question

我有一个普通的rubyclassEspresso::MyExampleClass.

module Espresso
  class MyExampleClass
    def my_first_function(value)
      puts "my_first_function"
    end

    def my_function_to_run_before
      puts "Running before"
    end
  end
end

使用 class 中的一些方法，我想执行类似于 ActiveSupport 回调 before_action 或 before_filter 的 before 或 after 回调.我想在我的 class 中添加这样的内容，它将运行 my_function_to_run_before 在 my_first_function:

之前

before_method :my_function_to_run_before, only: :my_first_function

结果应该是这样的：

klass = Espresso::MyExampleClass.new
klass.my_first_function("yes")

> "Running before"
> "my_first_function"

如何在 ruby class 中使用回调，例如 Rails 到运行每个指定方法之前的方法？

编辑 2：

感谢@tadman 推荐 XY problem。我们遇到的真正问题是 API 客户端的令牌过期。在每次调用 API 之前，我们需要检查令牌是否过期。如果我们有很多 API 的函数，那么每次检查令牌是否过期会很麻烦。

这里是例子class:

require "rubygems"
require "bundler/setup"
require 'active_support/all'
require 'httparty'
require 'json'

module Espresso

  class Client
    include HTTParty
    include ActiveSupport::Callbacks

    def initialize
      login("admin@example.com", "password")
    end

    def login(username, password)
      puts "logging in"
      uri = URI.parse("localhost:3000" + '/login')
      http = Net::HTTP.new(uri.host, uri.port)
      http.use_ssl = true
      http.verify_mode = OpenSSL::SSL::VERIFY_NONE
      request = Net::HTTP::Post.new(uri.request_uri)
      request.set_form_data(username: username, password: password)
      response = http.request(request)
      body = JSON.parse(response.body)
      @access_token = body['access_token']
      @expires_in = body['expires_in']
      @expires = @expires_in.seconds.from_now
      @options = {
          headers: {
              Authorization: "Bearer #{@access_token}"
          }
      }
    end

    def is_token_expired?
      #if Time.now > @expires.
      if 1.hour.ago > @expires
        puts "Going to expire"
      else
        puts "not going to expire"
      end

      1.hour.ago > @expires ? false : true
    end

    # Gets posts
    def get_posts
      #Check if the token is expired, if is login again and get a new token
      if is_token_expired?
        login("admin@example.com", "password")
      end
      self.class.get('/posts', @options)
    end

    # Gets comments
    def get_comments
      #Check if the token is expired, if is login again and get a new token
      if is_token_expired?
        login("admin@example.com", "password")
      end
      self.class.get('/comments', @options)
    end
  end
end

klass = Espresso::Client.new
klass.get_posts
klass.get_comments

Answer 1

一个简单的实现是；

module Callbacks

  def self.extended(base)
    base.send(:include, InstanceMethods)
  end

  def overridden_methods
    @overridden_methods ||= []
  end

  def callbacks
    @callbacks ||= Hash.new { |hash, key| hash[key] = [] }
  end

  def method_added(method_name)
    return if should_override?(method_name)

    overridden_methods << method_name
    original_method_name = "original_#{method_name}"
    alias_method(original_method_name, method_name)

    define_method(method_name) do |*args|
      run_callbacks_for(method_name)
      send(original_method_name, *args)
    end
  end

  def should_override?(method_name)
    overridden_methods.include?(method_name) || method_name =~ /original_/
  end

  def before_run(method_name, callback)
    callbacks[method_name] << callback
  end

  module InstanceMethods
    def run_callbacks_for(method_name)
      self.class.callbacks[method_name].to_a.each do |callback|
        send(callback)
      end
    end
  end
end

class Foo
  extend Callbacks

  before_run :bar, :zoo

  def bar
    puts 'bar'
  end

  def zoo
    puts 'This runs everytime you call `bar`'
  end

end

Foo.new.bar #=> This runs everytime you call `bar`
            #=> bar

这个实现中的棘手点是，method_added。每当一个方法被绑定时，method_added 方法就会被 ruby 使用该方法的名称调用。在此方法内部，我所做的只是名称修改并用首先运行回调然后调用原始方法的新方法覆盖原始方法。

请注意，此实现既不支持块回调也不支持超级 class 方法的回调。不过，它们都可以很容易地实现。

在普通 Ruby class 中使用方法回调

Using method callbacks in plain Ruby class

ruby

activesupport