Flex warning: variable has no type declaration

Question

I need to  dynamically create several Form or Panel, called MyForm1, MyForm2, MyPanel1, MyPanel2, ... They are different because of the children in the Form or Panel. I also added some addtional public methods (method1, method2 ...) to the <mx:Form> or <mx:Panel>.
I have a function, called myFactory,  that returns the MyForm1, MyPanel1... for me according to the input parameters. It is defined something like:
function myFactory(input:String):DisplayObject {
I tried two ways to call myFactory.
1.
var myViewObj:DisplayObject = myFactory(input:String); // no error. no warning.
myViewObj.method1(); // compilation error because DisplayObject dose not have method1
2.
var myViewObj = myFactory(input:String); // no error, but got warning: variable has no type declaration
myViewObj.method1(); // it works fine.
It looks like the type of myViewObj is the actual type of myFactory retures, which could be one of MyForm1, MyPanel1....
My questions are
1. Is there a way I can declara a type to myViewObj to get ride of  warning.
2. what type myViewObj should be called? generic type?

Answer 1

In case your custom Form and Panel components share same method names (with different functionality), you can create an Interface with the common methods declaration and have both components implement it.
This way you can declare the new interface as the returned type and invoke the common methods that it have.
Thia is sort of a Polymorphism technic, a subject where you can read more about in the following page -
http://en.wikipedia.org/wiki/Polymorphism_in_object-oriented_programming
Good luck!