Question

I have the following code:

class Number
 number = null
 constructor: (num) ->
  number = num
 getNumber: -> number

class Sequence
 numbers = []
 constructor: ->

 addNumber: (n) ->
  numbers.push new Number n

 displaySequence: ->
  for number in numbers
   alert number.getNumber()

seq = new Sequence()
seq.addNumber 1
seq.addNumber 2
seq.displaySequence()

The numbers array of seq should contains 2 Number object with value 1 and 2, but the result I’m getting is 2 and 2… Can someone shed me some light?

Answer 1

The problem is your number class which copiles to the following JavaScript. Where the variable number is stored in the scope instead of being member of the Number function:

Number = (function() {
  // number is stored in the scope not as a member of the prototype
  var number;

  number = null;

  // this is the function that will be return
  // so when ever you call it you override number
  function Number(num) {
    number = num;
  }

  Number.prototype.getNumber = function() {
    return number;
  };

  return Number;

})();

You have to make the number you wanna store to be a property of the class using @:

class Number
 constructor: (@num) ->
 getNumber: -> @num

which compiles to:

var Number;

Number = (function() {

  function Number(num) {
    //now num is stored in the returned function not in the scope of the parent function
    this.num = num;
  }

  Number.prototype.getNumber = function() {
    return this.num;
  };

  return Number;

})();