从coffeescript中的类的属性中的方法访问属性的属性

Question

I want to be able to access a property of a class property from a method of a class property.

// lets say
class foo
  constructor: () ->
  vars: {
    bar: "somevalue"
  },
  op: {
    baz: () ->
      #get the value of foo.vars.bar
  }

How do I do it, it returns undefined if i try foo.vars.bar

EDIT

Sorry for not making it so clear, I want

baz: () ->
  something = foo.vars.bar

Is there a simple way to do it, because

baz: () ->
   something = foo.prototype.vars.bar

works fine.

Answer 1

I can think of two ways you can do this: always access foo.vars via the foo prototype (as you've discovered) like this:

foo::vars.bar

( foo:: is a shortcut for foo.prototype in coffeescript)

Or you could ensure that the context of bar is bound to an instance of foo when it's called. One way to do this would be to bind it in the foo constructor:

class foo
  constructor: () ->
    @op.baz = @op.baz.bind @
  vars: {
    bar: "somevalue"
  },
  op: {
    baz: () ->
      console.log @vars.bar
  }

Which of these is most suitable probably depends on whether you want to use the same vars object across all classes or not. The second option probably isn't suitable if you want the context of baz to be something other than a foo instance.

Answer 2

One potential way is to have the parent instance variable defined in the scope:

class foo
  this_foo = null # So that the var is available everywhere within this context block
  constructor: () ->
    this_foo = @
  vars: {
    bar: "somevalue"
  },
  op: {
    baz: () ->
      this_foo.vars.bar
  }
console.log (new foo).op.baz() # => somevalue

Fiddle: http://jsfiddle.net/XL9aH/3/

This solution will allow this instance of foo, this_foo (rename to your liking) to be accessed in other ops as well without binding them or changing their value for this (or coffee-script @ ).