Hi,
> Tracing through the code, everything appears fine up to the point
> where I try to call the stored callback. This line:
>
> info.key.info.value(this));
>
> info.key and info.value are both valid objects, but nothing happens.
Your 'info.key' property is your observer, which I tend to suspect
doesn't then have a property called 'info' on it, but that's what
"info.key.info" retrieves. Then you retrieve the 'value' property from
that and try to call it ("info.key.info.value(this)"). You're also
passing in a 'this' value which refers to the browser window, whereas
I suspect you wanted to refer to the observable object.
I think this is what you meant:
observerInfo.each(function(info) {
info.value.call(info.key, this);
}, this);
...which will call the callback setting the observer as the context
(the 'this' value within the callback) and passing in the observed
object -- note that to do that, I had to pass 'this' into #each as its
second argument because otherwise context is lost when you call #each.
But the above, by itself, won't solve the problems because I think you
probably have an issue here:
> this.observableChanges.get(property).set(observer, callback);
Hash#set is documented as accepting a String for the key, but you're
passing in other kinds of objects, not just strings. You can't rely on
the key not getting converted to a string (a string that will probably
be "[Object]" or similar).
FWIW, I probably wouldn't use Hash for this at all, it's overkill for
the 'observableChanges' property and mis-matched for the values within
that. I'd probably just use a plain JavaScript object for
'observableChanges' using the property name as the key, with the value
being an array of tuples for the callbacks to make.
HTH,
--
T.J. Crowder
Independent Software Consultant
tj / crowder software / com
www.crowdersoftware.com
On Dec 3, 9:00 pm, Wil <wil.tur...@gmail.com> wrote:
> Hi all,
>
> I'm trying to implement a somewhat generic way for my controller
> objects to listen for changes to various properties of my model
> objects. I'm not a javascript expert, so there is quite possibly a
> Better Way™ of solving the bigger problem - I'm open to pointers in
> that direction, if my current approach is not a good idea.
>
> Here's the machinery I currently have in place:
>
> MyClass.prototype.observeValueChange = function(observer, property,
> callback) {
> if (this.observableChanges == null) this.observableChanges = new
> Hash();
> if (this.observableChanges.get(property) == null)
> this.observableChanges.set(property, new Hash());
> this.observableChanges.get(property).set(observer, callback);
>
> }
>
> MyClass.prototype.fireValueChanged = function(property) {
> if (this.observableChanges == null) return;
> var observerInfo = this.observableChanges.get(property);
> if (observerInfo == null) return;
> observerInfo.each(function(info) {
> info.key.info.value(this));
> });
>
> }
>
> Here's an example of registering to listen:
>
> objectOfMyObservableClass.observeValueChange(this, 'foo', function
> (destination) {
> alert("observed change in foo");
>
> });
>
> objectOfMyObservableClass.fireValueChanged("foo");
>
> Tracing through the code, everything appears fine up to the point
> where I try to call the stored callback. This line:
>
> info.key.info.value(this));
>
> info.key and info.value are both valid objects, but nothing happens.
>
> Thanks in advance!
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