Binding Mxml & ActionScript

Binding is one of the very useful feature in Flex. Though most intermediate programmers know how to bind a variable in mxml… most are clueless how to achieve this in AS. I’ll discuss both these aspects here.

Binding in MXML

Lets look at the following code…

<mx:TextInput id=”ti1″/>
<mx:Label id=”label1″ text=”{ti1.text}”/>

Here you are binding the text property of the TextInput to the label. So whatever you type in the textInput automatically reflects in the label. That’s the power of Binding…

Binding in AS

This is not as simple as binding in mxml. But it is simple enough…

The key to this is a class called BindingUtils in the mx.binding.utils package. You can use this class as below…

You have your components say in mxml as follows

<mx:TextInput id=”ti1″/>
<mx:Label id=”label2″/>

Now you impost the Binding utils class in the script tag

import mx.binding.utils.BindingUtils;

Then you use the bindProperty method to do the binding in AS as follows…

BindingUtils.bindProperty(label2,”text”,ti1,”text”);

This binds the ti1.text to label2.text. And you are set with your binding…

Binding is specially useful in data related components like List, DataGrid, Charts…etc. You can bind the dataProviders of these components to ArrayCollections or results of HTTPService objects, so that any change in data, immediately reflects in on the component.

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