Question

Say I have the following custom component:

<s:Group xmlns:fx="http://ns.adobe.com/mxml/2009" 
         xmlns:s="library://ns.adobe.com/flex/spark" 
         xmlns:mx="library://ns.adobe.com/flex/mx">
    <fx:Script>
    <![CDATA[
        [Bindable]
        public var prop:String;

        private function formatProp() : String {
            return "Hello, " + prop;
        }

    ]]>
    </fx:Script>

    <s:Label text="User: {prop}"/>
    <s:Label text="Greeting: {formatProp()}"/>
</s:Group>

If I add it to my application like this:

<local:MyComponent prop="Hello"/>

The result looks like:

User: Mark
Greeting: Hello, null

It seems Flex is setting prop on my custom component after it has already initialized the child labels, so it’s reliant on the property changed event to set the user label.

Is there an elegant way to make Flex wait for all of my component’s properties to be set before initially evaluating bindings?

Note: I realize the formatProp function is trivial and could be included inline, but this is just a simplified example.

Answer 1

it is not related to component livecycle, more to binding rules. Your function “formatProp” should recieve the parameter “prop” as a parameter in order to be called when the prop is changed. Try this code:

        private function formatProp(props:String) : String {
            return "Hello, " + props;
        }
        <s:Label text="Greeting: {formatProp(prop)}"/>