Determine the type of an object

[deejross]

I've been trying to figure this out for a while and would hope someone can help me. There's no real way to ask, so I have to ask with an example. Let's say I want to make a control that acts kind of like the form designer. At run-time, you can drag, pre-coded objects onto the control. Let's say I've pre-coded a few controls (GraphicsLabel GraphicsShape, etc.), and they all inherit my basic GraphicsObject class. I would need to keep those objects in a list somewhere, so I make an arraylist that holds all the objects drawn. Now, I want to enumerate through that list, so I do this:

For each obj as GraphicsObject in objList
...
Next

Which is a problem because I would need to interact with each object differently based on its type. So how would I tell if the current obj in the enumeration was a GraphicsLabel, or any other type of object that inherits GraphicsObject? This is kind of tough to explain and I hope it makes sense. Thanks in advance for your help.

 

[ManicCW]

I'm not sure to understand but is this something you can use:

For each obj as GraphicsObject in objList
If TypeOf obj is GraphicsObject Then
...
End If
Next

 

[deejross]

So, doing a For Each as a GraphicsObject, you can also evaluate if it's another type? I thought there was no way to tell what kind of object something was once it was added to an arraylist because it gets added as a System.Object.

If that's not the case, then technically I could do a For Each as System.Object, then do a If TypeOf obj is GraphicsLabel or TypeOf obj is GraphicsShape Then...

Am I correct?

 

[night_prince]

Hi
Im not sure but you can try this

Select Case TypeOf passedObject
 
Case Is GraphicShape.GetType
 
     ' What Do you want to do
 
Case Is GraphicLabel.GetType
 
' ......etc

Another Way:
if you want as an example :to get the area of each Shape
You Can Make an "interface " which has a function called :
GETArea()
and implements the interface in each Class that inherits GraphicObject Class

then you can call the function whatever the Object Be ??

Interface Graphic
Sub GetArea()
End Interface
 
 
'now in each control Do like this
 
Class LabelGraphic
Implements Graphic
 
Sub GetArea() implements Graphic.GetArea
  ' type some code here
 
End Sub
 
'now outside you can pass any kind of object that implements Graphic Interface
 
Sub DrawControl(object as Graphic)
Graphic.GetArea()
 
 
End Sub

Sorry for mistake but i hope this will help you