On 1 Apr 2008, at 23:35, Victor Mayevski wrote:

Can somebody please update the XOTcl tutorial/reference to explain in detail what abstract class is and how to use it (examples of usage)? I've been looking everywhere and can't find the info.

I'm not a core XOTcl developer, but the general case for abstract classes is that you want to have a superclass for a variety of other classes and this superclass provides some of the methods, but not all. The rest, or a small subset, can be specified as 'abstract' methods. With these only the 'style' of the method is described -- what arguments it takes, what it is named, perhaps what it returns and what it does. The sub-classes are then required to do the actual implementation of these methods.

So say you have a general 'GraphOb' class. It has an abstract method 'draw'. It cannot draw itself, or anything else, but it expects the sub-classes to implement this method. You might then have 'Rectangle' and 'Circle' which are subclasses of GraphOb and each of these have a 'draw' method which draws the rectangle or circle on to the screen.

Some classes might only have abstract methods...

Hope this explains it a bit.

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