ruby-on-rails - 检查 mixee 类上是否定义了方法？

Question

我们有一个模块来处理取消模型。它很干净，工作很好，但是我们遇到了一个问题，我们想要将它混合到一个已经定义了我们的模块方法(cancel! 等)的类中。

我们试图想出新的名字来避免冲突，但一切似乎都不太理想，我们喜欢调用 cancel! 的干净利落。因此，我们决定要执行以下操作:

def cancel!
  cancelly_stuff
  if class.parent.respond_to(:cancel!) super
end

但是，它是一个模块，所以我们将它混合到的类不是 class.parent。我无法用谷歌搜索如何引用模块的 mixee 类。

Answer 1

我对您的帖子给出了另一个答案，现在使用 prepend 而不是 include(仅适用于 ruby​​ 2.x)。第一个是包含在祖先链的顶端，因为第二个在类之后。

让我们看看它在 irb 控制台上是如何工作的:

~/rails/learn/ruby (main) > module A
~/rails/learn/ruby (main) |   def cancel!
~/rails/learn/ruby (main) |     puts 'cancel from m:A'
~/rails/learn/ruby (main) |     super if defined? super
~/rails/learn/ruby (main) |   end  
~/rails/learn/ruby (main) | end  
=> :cancel!
~/rails/learn/ruby (main) > class C
~/rails/learn/ruby (main) |   prepend A
~/rails/learn/ruby (main) |   def cancel!
~/rails/learn/ruby (main) |     puts 'cancel from c:C'
~/rails/learn/ruby (main) |   end  
~/rails/learn/ruby (main) | end  
=> :cancel!
~/rails/learn/ruby (main) > C.ancestors
=> [
    [0] #<Class:0x000000035421f0>::A,
    [1] #<Class:0x000000035421f0>::C < Object,
    [2] Object < BasicObject,
    [3] PP::ObjectMixin,
    [4] Kernel,
    [5] BasicObject
]
~/rails/learn/ruby (main) > C.new.cancel!
cancel from m:A
cancel from c:C
=> nil
~/rails/learn/ruby (main) > class D
~/rails/learn/ruby (main) |   include A
~/rails/learn/ruby (main) |   def cancel!
~/rails/learn/ruby (main) |     puts 'cancel from c:D'
~/rails/learn/ruby (main) |     super if defined? super
~/rails/learn/ruby (main) |   end  
~/rails/learn/ruby (main) | end  
=> :cancel!
~/rails/learn/ruby (main) > D.ancestors
=> [
    [0] #<Class:0x000000035421f0>::D < Object,
    [1] #<Class:0x000000035421f0>::A,
    [2] Object < BasicObject,
    [3] PP::ObjectMixin,
    [4] Kernel,
    [5] BasicObject
]
~/rails/learn/ruby (main) > D.new.cancel!
cancel from c:D
cancel from m:A
=> nil

希望对您的问题有所帮助。