Question

How to make method “btnClick” private?

class FirstClass
  constructor: ->
    $('.btn').click @btnClick

  btnClick: =>
    alert('Hi from the first class!')

class SecondClass extends FirstClass
  btnClick: =>
    super()
    alert('Hi from the second class!')

@obj = new SecondClass

http://jsfiddle.net/R646x/17/

Answer 1

There’s no private in JavaScript so there’s no private in CoffeeScript, sort of. You can make things private at the class level like this:

class C
    private_function = -> console.log('pancakes')

That private_function will only be visible within C. The problem is that private_function is just a function, it isn’t a method on instances of C. You can work around that by using Function.apply or Function.call:

class C
    private_function = -> console.log('pancakes')
    m: ->
        private_function.call(@)

So in your case, you could do something like this:

class FirstClass
    btnClick = -> console.log('FirstClass: ', @)
    constructor: ->
        $('.btn').click => btnClick.call(@)

class SecondClass extends FirstClass
    btnClick = -> console.log('SecondClass: ', @)

Demo: http://jsfiddle.net/ambiguous/5v3sH/

Or, if you don’t need @ in btnClick to be anything in particular, you can just use the function as-is:

class FirstClass
    btnClick = -> console.log('FirstClass')
    constructor: ->
        $('.btn').click btnClick

Demo: http://jsfiddle.net/ambiguous/zGU7H/