Say I have a Coffeescript class like this:
class Foo
aVar = 'foo'
someFunction = ->
anotherVar = 'bar'
Is there a way to set anotherVar as a class variable without having to declare it as null, like so:
class Foo
aVar = 'foo'
anotherVar = null
someFunction = ->
anotherVar = 'bar'
No, you can't. Let us look at a simple class:
class C
cv = null
m: -> cv
That is converted to this JavaScript:
var C = (function() {
var cv;
function C() {}
cv = null;
C.prototype.m = function() {
return cv;
};
return C;
})();
You'll notice that the "private class variable" cv is just a local variable inside the self-executing function that builds C. So, if we wanted to add a new "private class variable" to C, we'd have to open that anonymous function's scope again and add new variables. But there's no way to travel back in time and alter the scope of a function that has already executed so you're out of luck.
You don't have to define your anotherVar as null when you define it but you have to initialize it to something.
@; oh well!Have you ever heard about this keyword? :) CoffeeScript maps @ into this:
class Foo
aVar = 'foo'
someFunction: ->
@anotherVar = 'bar'
someFunction is mapped to a property of prototype of Foo. The code you've wrote above won't even work. Prototype functions can only access variables within this context. If you want to use private variables, then you have to define someFunction within a constructor of Foo with @ prefix.someFunction.