Re: [flexcoders] Alternative to Repeater

Sat, 07 Jan 2006 22:07:27 -0800

In a nutshell, DataSelector is a mixin.  A mixin adds methods and properties to a class at runtime.  Since you cannot do multiple inheritance in ActionScript, using a mixin is a way around that.  DataSelector adds dataProvider powers to a class:
 
DataSelector.initialize(YourClass);
 
Any class that utilizes DataSelector gets a length property.  DataSelector gives a class pretty much all the DataProvider methods (which are really proxies to the dataProvider it contains a reference to), length being one of them.  So:
 
yourComponent.length
 
is the same as:
 
yourComponent.dataProvider.length
 
 
Yes, modelChanged fires everytime you use a DataProvider method on a dataProvider or dataProvider component.
 
a = ["one", "two", "three"];
yourComponent.dataProvider = a;
 
a.addItem("cow"); // fires modelChanged
a.push("cheese"); // does not fire modelChanged
yourComponent.addItem("moo"); // fires modelChanged
 
ModelChanged actually has an object that is passed to it, the event object, that has information about what changed.  You can use a switch statement to know what changed, and how, and more intelligently draw your component.  A note; this is a fuoi$%(*)$% load of work.  If you don't believe me, go look in DataGrid.as.
 
So, to be lazy, I just ignore it and redraw everytime.  Keep in mind, even if you use the code above, it'll only redraw once:
- modelChanged fired for setting the dataProvider
- modelChanged fired for adding "cow" to it
- modelChagned fired for adding"moo" to it
 
Since I use a doLater, and only 1, it'll only redraw once per frame.
 
----- Original Message -----
Sent: Saturday, January 07, 2006 11:38 AM
Subject: Re: [flexcoders] Alternative to Repeater

Thanks for the help.
Couple of question
 
1 .What do you mean by - utilize Data Selector on that class ?
 
2. In the redrawForm method what does the value "length" represent.
If it is the length of the dataProvider, am not clear how that was established
 
3. Does "modelChanged" fire every time the dataProvider changes?
If so seems like it would redraw the entire form even if only one item in the array changed (say using addItem).
 
Thanks,
 
- superabe
 
On 1/7/06, JesterXL <[EMAIL PROTECTED]> wrote:
You basically do:
- create a new abstract base class for your component as ActionScript
- utilize DataSelector on that class
- extend that class in a new file
- have the new file do something like this
 
function modelChanged()
{
    cancelAllDoLaters();
    doLater(this, "redrawForm");
}
 
function redrawForm()
{
    canvas_mc.destroyAllChildren();
    var i:Number = length;
    while(i--)
    {
        var item:Object = getItemAt(i);
        canvas_mc.createChild(SomeComponent);
    }
}
 
 
What is happening here is whenever the dataProvider changes, the form is redrawn.  It's only redrawn once per frame in case dataProvider has 50 billion changes.
 
If you see the createChild call for the canvas, basically you could put in logic, say, to create images, and then call load on them based on the url for the current item.
 
Then, you can finally use that AS component as MXML elsewhere.  Make sense?
 
 
----- Original Message -----
Sent: Saturday, January 07, 2006 11:09 AM
Subject: [flexcoders] Alternative to Repeater

 
Is there an alternative to using a Repeater , that I could make use of in my component (AS based).
For e.g.
 
Say I have a component called "Comp"
 
Comp.mxml (Pseudo-code)
===========
<mx:VBox>
  <mx:Script>
   
    public var dp:Array;
  </mx:Script>
 
  <mx:Repeater dataProvider="{dp}">
    <mx:Image source="{currentItem.url}"/>
  </mx:Repeater>
 
</mx:VBox>
 
Comp is used in Main.mxml and the dataprovider for Comp is set in Main.mxml.
Main also may add and remove items from the the dataprovider for Comp on subsequent events.
 
I would like to write Comp as an Actionscript class and avoid a Repeater all together.
I may be missing something really obvious, but how would I do that ?
 
TIA,
 
- superabe
 
 
 
 


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