在CoffeeScript中尝试在类中调用方法（@_methodName）时，它返回undefined

Question

I'm trying to use underscore's debounce function in my code, and I'm passing a method of my class as the first parameter, but _.debounce is telling me that I'm passing an undefined parameter where the function should be.

class SomeClass

  click: _.debounce @_save, 600

  _save: =>
    # Save logic

On the other hand, If I do it like this, it works, but this solution seems kind of ugly.

class SomeClass

  click: _.debounce ( -> 
    @_save()
  ), 600

  _save: =>
    # Save logic

When I check the generated JS source of both functions, it seems like both should work fine, don't know if I'm missing something from CoffeeScript here.

Answer 1

CoffeeScript compiles:

click: _.debounce @_save, 600

into:

SomeClass.prototype.click = _.debounce(SomeClass._save, 600);

Notice how _save method is a static property of SomeClass , ie it is not on the prototype because in your declaration @ refers to the class itself, not its instance.

Alternatively you can declare your click function in the constructor:

constructor: ->
  @click = _.debounce @_save, 600

This will ensure you have a debounced function per instance, and not a shared one.

Answer 2

I think, you should try something like this instead:

class SomeClass
  constructor: ->
    @click = _.debounce @_save, 600

  _save: =>
    # ...