Apache – How to cast one Flex object as a derived type

apache-flex

Here's the example:

var cartesian:CartesianChart = new CartesianChart(); 
cartesian.width = 100;
var column:ColumnChart = new ColumnChart();
column = cartesian as ColumnChart;

Why does this not work? "column" ends up null. ColumnChart is a derived class of CartesianChart, so I would have thought I'd end up with a ColumnChart with a width of 100.

Best Answer

ColumnChart extends CartesianChart? I don't believe you can cast an object from a parent class to an object of it's child class. Your best bet is to write a class function on ColumnChart called something like copyFromCartesianChart that takes the CartesianChart object as a param and gets and sets all the props you need.

Related Solutions

Apache – How to introspect a Flex component before adding it to display

There are multiple ways of component instantiation in Flex.

If you use the constructor in ActionScript, you get a bare metal object where nothing but construction of the object itself has been completed. In particular, this new object has not yet instantiated its child views, that's why you don't see anything when you look at the results of getChildren().

If you write down your component in MXML, the MXML compiler creates ComponentDescriptors instead of "real" objects. These hold all information you specified for the object in MXML (properties, bindings, event handlers etc), and the runtime uses them to create real objects at the appropriate time. "Appropriate time" usually means "when the object is added to the display list". That's why you only see children after calling addChild() (technically, not immediately after calling addChild(), but only after your newly instantiated object has dispatched its creationComplete event).

How to specify height and width of flex alert box in css

You can do it Using Style + Code like this

Define Style Properties as

Alert {

        height:300;
        weight:300;
    }

Note: height and weight are not default style of Alert

Using them in Code as

var alert:Alert = Alert.show("Hello World");
alert.explicitHeight = Number(alert.getStyle("height"));
alert.explicitWidth = Number(alert.getStyle("weight"));

Working example of Flex3 is

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"
    creationComplete="{show()}">
    <mx:Style>
        Alert {

            height:300;
            weight:300;
        }
    </mx:Style>
    <mx:Script>
        <![CDATA[
            import mx.controls.Alert;
            private function show():void
            {
                var alert:Alert = Alert.show("Hello World");
                alert.explicitHeight = Number(alert.getStyle("height"));
                alert.explicitWidth = Number(alert.getStyle("weight"));
            }
        ]]>
    </mx:Script>
</mx:Application>

Explanation

Since Alert Control by default not support height and weight style, so example used them just for holding user defined values as variable.

In routine to display Alert/Popup on screen Static method show of class Alert is used, which returns the instance/object of created/active Alert/Popup, using this refrence its properties can be manipulated at runtime as done in above example i.e. explicitHeight and explicitWidth.

Hopes that Help

Best Answer

Related Solutions

Apache – How to introspect a Flex component before adding it to display

How to specify height and width of flex alert box in css

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