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24. Sept. 2011 · The problem statement you make in the updated answer is already solved by 9.2p9 (see accepted answer's comment section). 9.2p9 forbids to put "override" on non-virtual functions. The only problem I see is the example, and it can be solved by just putting "virtual" before the function "f" in "D".
- What if B::f would not have been marked virtual? Is the program ill-formed, then? Yes, it is. Because in order to override something, that some...
- If B:f was non-virtual, then both D:f functions would be ill-formed.
- Yes, the program is ill formed when override is added to any non-virtual function. Generally, functions with differing signatures (overloaded), a...
The non-virtual interface pattern (NVI) controls how methods in a base class are overridden. Such methods may be called by clients and overridable methods with core functionality. [1] It is a pattern that is strongly related to the template method pattern .
3. Feb. 2016 · My main confusion is how does (during the upcasting) the derived class object provide information about the base class non virtual function since it only has information of base as Base::b_value. c++. virtual-functions. Share. Improve this question. edited Feb 3, 2016 at 8:48. asked Feb 3, 2016 at 8:21.
Calling a virtual function is fast — almost as fast as calling a non-virtual function. You don’t get any additional per-call overhead no matter how deep the inheritance gets. You could have 10 levels of inheritance, but there is no “chaining” — it’s always the same — fetch, fetch, call.
Thus if the first non-inline virtual function in Fred is wilma(), the compiler will put Fred’s virtual table in the same compilation unit where it sees Fred::wilma(). Unfortunately if you accidentally forget to define Fred::wilma() , rather than getting a Fred::wilma() is undefined, you may get a “ Fred ’s virtual table is undefined”.
7. Mai 2019 · The NVI, or Non-Virtual Interface design pattern, is in a way a mechanism to extend the functionality of a function, just alike inheritance allow classes to be extended. It’s one way of implementing the strategy pattern. Imagine that you have two processes that look a bit the same: void process_a() { step1(); step2_variant_a(); step3(); }
16. Aug. 2016 · Perhaps I am confused about (a) using a class safely without a virtual destructor versus (b) safety-by-design / I cannot get it wrong. In case (a), to use safely, only stack allocate. This requires discipline! In case (b), either add a virtual destructor in Base or force stack allocation via a private constructor and public static ...
