如何在CoffeeScript中访问类方法？

Question

I am prefacing this: I am new to CoffeeScript and JavaScript prototyping as a whole.

That being said, I am trying to create a new Object of a class in CoffeeScript, and then call a getter to retrieve the variable but what happens is I get an 'undefined' response instead. What am I doing wrong, or how I should I approach this. I am fairly new and trying to follow the KISS standard.

class TestHandler
  constructor: ->
  testArray = []
  getTestArray: ->
    @testArray

tH = new TestHandler()
tH.testArray.push 1 #testArray returns undefined
tH.getTestArray().push 1 #getTestArray returns undefined
console.log tH.getTestArray()

Answer 1

When you create a class in CoffeeScript every metod you list down there goes to the prototype property (in this case TestHandler.prototype ) and therefore is shared among instances of that class, however every other property, will be either a member of TestHandler itself (if name prepended with @ ) or a private variable of scoped to a function that class will eventually be compiled to (like was with your testArray = [] ). It means, that your tH won't have a property called testArray . If you wanted it to be an own property of the each instance, put this into the constructor:

class TestHandler
    constructor: ->
        @testArray = []
    getTestArray: ->
        @testArray

tH = new TestHandler()
tH.testArray.push 1 #now everything works
tH.getTestArray().push 1
console.log tH.getTestArray()

---

Generally, where the property will land depends on how you write in the class declaration. Look at this CS code

 class TestHandler
   constructor: ->
     @testArray = [] #1
   testArray = [] #2
   @testArray = [] #3
   getTestArray: -> #4
   testArray: [] #5

and the code that it compiles to:

 var TestHandler;

 TestHandler = (function() {
   var testArray;

   function TestHandler() {
     #1 @thisArray in constructor becomes instance property accessor
     this.testArray = [];
   }

   #2 becomes a local variable, not available outside this function
   testArray = [];

   #3 becomes a "static" property
   TestHandler.testArray = [];

   #4 is a method that goes to the prototype, so that it can be shared with all instances
   TestHandler.prototype.getTestArray = function() {};

   #5 is a property that goes to the prototype and can be shared with all instances (although this shouldn't be done unless you know what you do)
   TestHandler.prototype.testArray = [];

   return TestHandler;

 })();