Question

来自：http://cheind.blogspot.com/2008/12/method-hooks-in-ruby.html

我有

# Contains methods to hook method calls
module FollowingHook

  module ClassMethods

    private

    # Hook the provided instance methods so that the block 
    # is executed directly after the specified methods have 
    # been invoked.
    #
    def following(*syms, &block)
      syms.each do |sym| # For each symbol
        str_id = "__#{sym}__hooked__"
        unless private_instance_methods.include?(str_id)
          alias_method str_id, sym        # Backup original 
                                          # method
          private str_id                  # Make backup private
          define_method sym do |*args|    # Replace method
            ret = __send__ str_id, *args  # Invoke backup
            block.call(self,              # Invoke hook
              :method => sym, 
              :args => args,
              :return => ret
            )
            ret # Forward return value of method
          end
        end
      end
    end
  end

  # On inclusion, we extend the receiver by 
  # the defined class-methods. This is an ruby 
  # idiom for defining class methods within a module.
  def FollowingHook.included(base)
    base.extend(ClassMethods)
  end
end

然后我有一个类似的课程：

class User
  def self.get
   #class method
  end
  def name
   #instance method
  end
end

在另一个位置/文件中，我重新打开User类并挂钩

class User
  include FollowingHooks # include the hook module
  following :name do |receiver, args|
   #do something. This works!!
  end
  following :get do |reciever, args|
   #do something. THIS DOESNT WORK
   # Which is to be expected looking at the FollowingHooks module definition.
  end
end

挂钩任何实例方法都有效。然而，尝试挂钩类方法什么也没做，我得到了，因为FollowingHooks模块没有实现它。我如何实现类方法的钩子？我完全无能为力。

Answer 1

您需要在Class上包含FollowHook代码，然后调用以下内容以使其适用于类方法。

Class.send(:include, FollowingHook)
class User
  class << self
    following :get do |reciever, args|
      # Your awesome code here
    end
  end
end

修改

这是我完整的工作解决方案，遵循这一建议：

# Contains methods to hook method calls module FollowingHook module ClassMethods private # Hook the provided instance methods so that the block # is executed directly after the specified methods have # been invoked. # def following(*syms, &block) syms.each do |sym| # For each symbol str_id = "__#{sym}__hooked__" unless private_instance_methods.include?(str_id) alias_method str_id, sym # Backup original # method private str_id # Make backup private define_method sym do |*args| # Replace method ret = __send__ str_id, *args # Invoke backup block.call(self, # Invoke hook :method => sym, :args => args, :return => ret ) ret # Forward return value of method end end end end end def self.included(base) base.send(:extend, FollowingHook::ClassMethods) end end class User def self.foo puts "foo" end def bar puts "bar" end end # You can put this in the class << self block if you prefer that the # methods only be available on the User class. Class.send(:include, FollowingHook) class User include FollowingHook following :bar do |receiver, args| puts receiver.inspect end class << self # If you prefer only the User class include FollowingHooks, use the # following instead of including them in Class. # include FollowingHook following :foo do |receiver, args| puts receiver.inspect end end end User.foo #=> # foo # User User.new.bar #=> # bar # #<User:0x338d9d>

Answer 2

嗯，这很有效。

    def following_c(*syms, &block)
      metaclass = (class << self; self; end)
      syms.each do |sym|
        str_id = "__#{sym}__hooked__"
        unless metaclass.send(:private_instance_methods).include?(str_id)
          metaclass.send :alias_method, str_id, sym        

          metaclass.send :private, str_id                  
          metaclass.send :define_method, sym do |*args|    
            ret = send str_id, *args 
            block.call(self,
              :method => sym, 
              :args => args,
              :return => ret
            )
            ret 
          end
        end
      end
    end

Ruby：如何挂钩类方法

2 个答案: