In our application, sometimes we need to keep the same object in several different places. Of course, we can create our own logic to produce a unique id for each objects. But Flex has contained a convinient way for us to complete this type of task.

First of all, we need to implement the mx.core.IUID interface, and then, we can use mx.core.UIDUtil.createUID function to generate the unique id for our object in our class’s constructor. This method will create a 32 bit hex string like:

E4509FFA-3E61-A17B-E08A-705DA2C25D1C

Here is the example:

package {
import mx.core.IUID;
import mx.utils.UIDUtil;
[Bindable]
public class Message implements IUID {
public var messageStr:String;
public var fromID:String;
private var _uid:String;
public function Message() {
_uid = UIDUtil.createUID();
}
public function get uid():String {
return _uid;
}
public function set uid(value:String):void {
// Since we'vealreadycreatedtheid,there's
//nothing to be done here, but the method is
//required by the IUID interface
}
}
}

I met a problem in my development of a Flex library recently. The library is a set of components for drawing topological diagram. My problem was that I can’t drag and drop a component in a Group container which was nested in anthor one. This made me feel headache for two days on this odd behaviour, even it worked fine if a use BorderContainer instead of Group. I searched in google about it, but no good news.

I have to start a discussion on a Chinese forum to discus with that, and no good luck, too. At last, I asked that question on Adobe Flex forum. After one day waiting, someone replied my post, he let me try to listen the dragEnter and dragDrop events in the parent Group container, not to listen them in the nested one. I followed his advice and modified my code. It worked. I could drag and drop components in a nested Group container, that was just what I want. I want to appreciate that guy again here. He really did me a great favour.

I’m using Flex 4 to upgrade a project in my work these days. Cause I have used Flex 3 for a long time in developing, Flex 4 really set a huge gap for me to adapt it immediately. I will write some articles about it in my learning progress.

First, I’ll record something about CSS in Flex 4 that I met in work. In Flex 4, We must declare namespaces if you want to customize the look of the Spark and Halo components like

@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/halo";

Now I can set a style of the component by prefix “s” or “mx”, The following style set the font color of  TextInput:

s|TextInput {
	color: #000000;
}

After then, I’ll talk about the validators’ error tip style, We can set the errorTip style like

.errorTip {
	fontSize: 12;
}

This set the error tips’ font size to 12.

OK, I’ll post some new articles about my experience on learning Flex 4 in the near future. If I make some mistakes or you have something to discus with me, please let me know.