This design is called composition because the existing class becomes a component of the new one. Each instance method in the new class invokes the corresponding method on the contained instance of the existing class and returns the results. This is known as forwarding, and the methods in the new class are known as forwarding methods. The resulting class will be rock solid, with no dependencies on the implementation details of the existing class.
It doesn’t exactly ‘solve’ the access to private members/methods problem. It forces you to reimplement them yourself, which you can then debate the merits of.
Definitely can work when you’re augmenting a class. Harder when trying to change one small part of its existing behavior.
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Robert
