Question

In CoffeeScript, if I define an instance property in a class constructor, that property can refer to other instance properties in its definition, for example:

class Foo
    constructor: (data) ->

        @One = 1

        @Two = @One + 1

But what about instance properties declared at the class level? The following does not work:

class Foo

    One: 1

    Two: @One + 1

In that context, the @ symbol refers to the ‘class’ itself, not the instance. Likewise simply removing the @ does not work.

Is there a way that one instance property declared at the class level can refer to another instance property in its definition?

Answer 1

When you say this:

class Foo
    one: 1

You’re setting one on Foo‘s prototype so you just have to look at @‘s prototype to get back to where one is:

class Foo
    one: 1
    two: @::one + 1

Demo

Note that this even works with subclasses so you do this:

class Pancakes extends Foo
    three: @::two + 1

and you’ll get the expected three.