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  • Roberto Orsini thinks this is interesting:

A mixin class is a class that’s intended to provide an optional interface or functionality to other classes. It’s similar to an abstract class in that it’s not intended to be instantiated. Mixin classes require multiple inheritance

From

Cover of Design Patterns: Elements of Reusable Object-Oriented Software

Note

Finalmente una definizione precisa e chiara di cos'è un mixin!