Hi,
When you use object literal notation, the right-hand side of an
initialization (the bit after the colon [:]) is evaluated when the
literal is evaluated, and then the *value* of the result is used to
initialize that property on the object created by the literal (the
options object you're passing into `Class.create`). So `this.foo` is
evaluated in the context of the code calling `Class.create`, and its
*value* is used to initialize `bar`.
This may be easier to understand if we take a simpler example:
var alpha, beta;
alpha = 5;
beta = {
key: alpha
};
What's the value of `beta`'s `key` property? Is it `alpha`, or `5`?
The answer of course is that it's `5`; when the object literal was
evaluated, the *value* of `alpha` was used to initialize `key`, not a
reference to `alpha`.
Similarly:
var gamma, delta;
gamma = {
key: 5
};
delta = {
key: gamma.key
};
Again the value of `delta`'s `key` property is `5`; there's no link to
`gamma` or its `key` property.
So let's go back to your `bar` initialization:
var baz = Class.create({
bar: this.foo,
foo: function() {
alert('I am foo and bar!');
}
});
What's the value of `bar`? Right, whatever the value of `this.foo` is
as of when you call `Class.create`. The `this` has nothing to do with
an instance of your class, it's whatever `this` is for the code that's
*calling* `Class.create`.
HTH,
--
T.J. Crowder
Independent Software Consultant
tj / crowder software / com
www.crowdersoftware.com
On May 21, 9:39 pm, blechler <[email protected]> wrote:
> Hi all,
>
> Given the code:
> -------------------------------------------
> var baz = Class.create({
> bar: this.foo,
>
> foo: function() {
> alert('I am foo and bar!');
> }
>
> });
>
> myObj = new baz();
> -------------------------------------------
> I would expect that:
> myObj.bar();
>
> would pop up the alert, but it turns out that myObj.bar is undefined.
> Must I write it like:
>
> bar: function() { this.foo(); }
>
> Any insight would be appreciated.
>
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