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by luiz-pv9
4711 days ago
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About the square/rectangle example, what would be the solution? The Square subclass should not verify equality with width and height or it should not even exist? Or something else? -- edit
Wikipedia:
If Square and Rectangle had only getter methods (i.e., they were immutable objects), then no violation of LSP could occur. |
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Yeah, this is the fundamental problem; mutable objects tend to result in LSP violations when class heirarchies follow common sense is-a relationships, but mutating operations are not limited to those (if any exist) that preserve identity.
A corollary to this is that the use of default constructors very often accompanies LSP violations, as it usually implies all of the object's state is subject to mutating operations.