Question

I’m very new to Flex 4.5 and I created a class (Project.as) with the following code in it:

package classes
{
    public class Project
    {
        public var projectName:String;
        public var description:String;
        public var fileLoc:String;

        public function Project()
        {
            // This is the constructor  
        }

        public function SayHello() {
            import mx.controls.Alert;
            Alert.show('howdy!','Greeting');
        }
    }
}

In my main.mxml file, I have the following code:

<fx:Script>
    <![CDATA[
        import classes.Project;             
        import mx.controls.Alert;

        public var aProject:Project = new Project;
        aProject.SayHello();
    ]]>
</fx:Script>

And Flex Builder is saying this:

1120: Access of undefined property aProject.

Why is it telling me this, and how can I fix it? I don’t see why it’s not working.

Answer 1

Lots of issues here.

First, I have never seen anyone put import statements inside a method. Usually they are put between the package and class definition:

package classes
{
   import mx.controls.Alert;

    public class Project
    {
        public var projectName:String;
        public var description:String;
        public var fileLoc:String;

        public function Project()
        {
            // This is the constructor  
        }

        public function SayHello() {
            Alert.show('howdy!','Greeting');
        }
    }
}

Second; the line of ActionSCript code that you write to call a method on your class instance should be placed inside a method; not “random”. Like this:

<fx:Script>
    <![CDATA[
        import classes.Project;             
        import mx.controls.Alert;

        public var aProject:Project = new Project;
        protected function sayHello():void{
          aProject.SayHello();
        }
    ]]>
</fx:Script>

Some way you’ll want to call that method. A commenter on the original post suggested using creationComplete, which would work. However, you should be cautious about using creationComplete for “constructor-style” code in an MXML Component. preinitialize is better, and the event will fire right after the actual constructor runs. If you need to access any MXML children, have your code in an initialize event handler which runs right after createChildren() runs.

creationComplete handlers execute right after the component finishes initializing; and people often do things in creationComplete that make the component go through it’s Lifecycle again, updating the display list.