Question

有人可以帮我修改为intercepting instance method calls提供的答案，以便它可以使用类方法调用，还是类和实例方法调用？根据我对Ruby的元编程知识的有限知识，我想它可能与使用class << self在某个地方打开单例类有关，但是我已经尝试用这个代码在各个地方做这个，我可以似乎没弄明白。但是，如果不是直接回答，你能否为我提供正确的方向？除非我完全超出自己的深度，否则我很喜欢为自己搞清楚事情。谢谢！

Answer 1

以下是我根据您提供的链接中的答案修改的解决方案。我将钩子逻辑从超类移到了一个单独的模块，这样当一个类需要钩子时，它只需要包含或扩展该模块并调用钩子方法。

before_each_method type, &block - type可以是:class或:instance，该块是每个方法之前要执行的代码。该块将在某些环境下进行评估，即例如方法，块中的self是实例;对于类方法，块中的self是类。
before_class_method &block - before_each_method :class, &block
before_instance_method &block - before_each_method :instance, &block

module MethodHooker
  def self.included(base)
    base.extend(ClassMethods)
  end
  def self.extended(base)
    base.extend(ClassMethods)
  end
  module ClassMethods
    def before_each_method type, &block
      singleton = class << self; self; end
      case type
      when :instance
        this = self
        singleton.instance_eval do
          define_method :method_added do |name|
            last = instance_variable_get(:@__last_methods_added)
            return if last and last.include?(name)
            with = :"#{name}_with_before_each_method"
            without = :"#{name}_without_before_each_method"
            instance_variable_set(:@__last_methods_added, [name, with, without])
            this.class_eval do
              define_method with do |*args, &blk|
                instance_exec(name, args, blk, &block)
                send without, *args, &blk
              end
              alias_method without, name
              alias_method name, with
            end
            instance_variable_set(:@__last_methods_added, nil)
          end
        end
      when :class
        this = self
        singleton.instance_eval do
          define_method :singleton_method_added do |name|
            return if name == :singleton_method_added
            last = instance_variable_get(:@__last_singleton_methods_added)
            return if last and last.include?(name)
            with = :"#{name}_with_before_each_method"
            without = :"#{name}_without_before_each_method"
            instance_variable_set(:@__last_singleton_methods_added, [name, with, without])
            singleton.class_eval do
              define_method with do |*args, &blk|
                instance_exec(name, args, blk, &block)
                send without, *args, &blk
              end
              alias_method without, name
              alias_method name, with
            end
            instance_variable_set(:@__last_singleton_methods_added, nil)
          end
        end
      end
    end
    def before_class_method &block
      before_each_method :class, &block
    end
    def before_instance_method &block
      before_each_method :instance, &block
    end
  end
end

class Test
  extend MethodHooker
  before_each_method :instance do |method, args, block|
    p [method, args, block]
    puts "before instance method(#{method}) #{@var}"
  end
  before_class_method do |method, args, block|
    puts "before class method(#{method}) #{@class_instance_var}"
  end
  @class_instance_var = 'stackoverflow'
  def initialize
    @var = 1
  end
  def test(a, b, c)
    puts "instance method test"
  end
  def self.test1
    puts "class method test"
  end
end

Test.new.test(1, "arg2", [3]) {|t| t}
Test.test1

输出类似于：

[:initialize, [], nil]
before instance method(initialize)
[:test, [1, "arg2", [3]], #<Proc:0x00000001017d5eb8@/Users/test/before_method.rb:88>]
before instance method(test) 1
instance method test
before class method(test1) stackoverflow
class method test

如何拦截类方法调用，而不仅仅是实例方法调用

1 个答案: