It depends...
...on the data object. Is it bindable? If so, does it really need to
be?
Let's say you have a person Object { firstName: "Alex", lastName:
"Harui"}. Not bindable. It becomes the data property of the renderer
and you want to map components in your renderer to it.
If you do:
<mx:Label text="{data.firstName"} />
you will get warnings as the firstName property is not bindable. So the
important question is: Does it need to be bindable? Is the firstName
property of an object going to get modified in a way that won't refresh
the List? Usually not, but sometimes, some other part of the UI is
binding to list.selectedItem.firstName which will still work as it will
trigger on a change to selectedItem, but if you are editing items in the
list and changing the firstName, then selectedItem will not change and
other UI will not update.
If it doesn't need to be bindable, then I'd just call
invalidateProperties and stuff the fields in commitProperties. The
speed difference will probably not be obvious, but it should be less
code and run slightly faster and you won't get warnings. If the data
object does need to bindable, then you might as well hook up with
binding if it is just a couple of bindings and the logic is simple. If
you already have a commitProperties method, I would probably not use
binding and map the data object fields in commitProperties because in
most cases, when the fields change in the person object, the entire data
property gets re-assigned due to the way most lists update their
renderers.
________________________________
From: [email protected] [mailto:[EMAIL PROTECTED] On
Behalf Of Amy
Sent: Thursday, May 29, 2008 8:13 PM
To: [email protected]
Subject: [flexcoders] Which is more expensive: binding or setting
Hi, all;
I have an itemRenderer based (sort of) on the checkBox Header
Renderer described here:
http://www.returnundefined.com/2006/11/creating-truly-reusable-
<http://www.returnundefined.com/2006/11/creating-truly-reusable->
renderers-with-classfactory
I'm using BindingUtils to bind to a property of an object I am
passing in. This property is the month number of the month that is
currently being displayed in a calendar page so that days prior to
the first of the month and after the last of the month can have a
different styleName.
However, I could probably add that to the code in commitProperties()
that sets the styleName based on checking the month of the date
property of the data variable against the month property that is set
automagically through BindingUtils.bindProperty(). Alternatively, I
could add more binding expressions to handle the other settings I'm
doing in commitProperties. I'd like to develop a more uniform
approach instead of the hodgepodge I have now.
The question is, which will perform better, binding or setting in
commitProperties()?
Thanks;
Amy
