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Call subclass variables from superclass

John Lockheart
Ranch Hand

Joined: Oct 13, 2006
Posts: 115
I understand how to call superclass variables from a subclass. But what if I wanted to call subclass variables from the superclass. Or even sub subclass variables (a subclass inside a subclass of the superclass) from a superclass. I want to reach down the Hierarchy for variables as opposed to reaching up (like when using super). How do I do that? Or is it not possible because the super class can't inherit any of the subclass variables? I'll use examples from the program i've been working on. I know there's supposed to be more code but I just slapped that together.

mohsen fakhari
Greenhorn

Joined: May 04, 2003
Posts: 25
Hi
When you modify a variable of Threat from Virus,in fact you modify a variable of Virus itself,because Virus instances do have all variables of Threat.
But speaking about a Threat instance,Virus is completely stranger whom it knows nothing about.
marc weber
Sheriff

Joined: Aug 31, 2004
Posts: 11343

On the surface, that's a reasonable question. But consider these issues:
  • How would a superclass "know" what subclasses are extending it?
  • If it did know, how might a superclass decide which of these subclasses to try to get a value from?
  • More fundamentally, what could a superclass do with a value from a subclass? In other words, why would the state of a subclass be of any concern to a superclass?


  • "We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer
    sscce.org
    Garrett Rowe
    Ranch Hand

    Joined: Jan 17, 2006
    Posts: 1296
    If these behaviors should be common to all sub classes, then you can move the behaviors there:

    This forces the subclasses to implement behavior that can be used by the superclass. Polymorphism.
    [ January 27, 2007: Message edited by: Garrett Rowe ]

    Some problems are so complex that you have to be highly intelligent and well informed just to be undecided about them. - Laurence J. Peter
     
    It is sorta covered in the JavaRanch Style Guide.
     
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