The Brittleness Of Type Hierarchies

Re:The Brittleness Of Type Hierarchies by SoftwareMaven on Tuesday May 08, 2012 @01:23PM (#3944749)

While I agree with you about the Liskov Substitution Principle, I don't think that would have helped in this example. If your assumptions about the behavior of the base classes are wrong, your code is wrong. Substitute a wrong super-class for a wrong sub-class, and it's still wrong.

What the LSP does do, though, is help you know when you really shouldn't be subclassing things. If your implementation leaks beyond the class interface, it shouldn't be a subclass.

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Re:The Brittleness Of Type Hierarchies by bunderbunder on Tuesday May 08, 2012 @01:38PM (#3944853)

Agreed that it isn't a magic fix. I was only hoping that bringing such a restriction to the forefront of programmers' minds would encourage them to be a little bit more diligent about deciding what's really an essential feature of a category before they start to cut code.

It's all too easy to fall into the trap of automatically pushing things up to the superclass without thinking first. "I might want this elsewhere" is a common way to look at it. Following LSP encourages one to think, "I might get stuck with this" instead.

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