Polymorphism - explanation?

[TheRobster]

Hi,

Can someone point me in the direction of an article that explains what polymorphism is with regards to its use in VB.Net?

I don't need to know how to use it.......yet......I just need a clear explanation as to what it is. Please bear in mind that I've only been learning VB for a few weeks and so don't want to be baffled by a load of technical talk!

Thanks
-Rob

[Edneeis]

http://www.vbforums.com/showthread.p...hreadid=288661

[wossname]

One of the notions of Polymorphism (Which literally means many shapes) if this.

Class Mouth
    Sub Speak()
        Console.WriteLine("Hello!")
    End Sub
 
    Sub Speak(ByVal Words As String)
        Console.WriteLine(Words)
    End Sub
 
    Sub Speak(ByVal Number As Integer)
        Console.WriteLine(Number)
    End Sub
End Class
 
...
 
Sub Main()
    Dim x as Mouth = new Mouth
    x.Speak("My Name is X") 'will automatically call the second version of Sub Speak()
End Sub

The framework knows what kind of data is being passed into the Speak sub and chooses the right variant to do the job.

But that is only a simple example. Inheritance can expand on this as can Encapsulation.

NOTE: You might also notice that Console.Writeline() is called using the same technique, the framework knows what data is incoming and acts accordingly.

[MrNorth]

If you want a more hands-on usage of polymorphism, the GOF pattern "state" uses it... Check out the definition of that pattern... It shows quite well how polymorphish works in practice.

kind regards
henrik