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Sep 24, 2011 · If a virtual function is marked with the virt-specifier override and does not override a member function of a base class, the program is ill-formed. [ Example: struct B { virtual void f (int); }; struct D : B { void f (long) override; // error: wrong signature overriding B::f void f (int) override; // OK }; What if B::f would not have been ...
- 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 somethin...
- 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), are...
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.
- Intent
- Motivation
- Solution and Sample Code
- Consequences
- Related Idioms
- References
To modularize/refactor common before and after code fragments (e.g., invariant checking, acquiring/releasing locks) for an entire class hierarchy at one location.
Pre- and post-condition checking is known to be a useful object-oriented programming technique particularly at development time. Pre- and post-conditions ensure that invariants of a class hierarchy (and in general an abstraction) are not violated at designated points during execution of a program. Using them at development time or during debug buil...
Non-Virtual Interface (NVI) idiom allows us to refactor before and after code fragments at one convenient location - the base class. The NVI idiom is based on 4 guidelines outlined by Herb Sutter in his article named "Virtuality". Quoting Herb: 1. Guideline #1: Prefer to make interfaces nonvirtual, using Template Method design pattern. 2. Guideline...
Using the NVI idiom may lead to fragile class hierarchies if proper care is not exercised. As described in , in Fragile Base Class (FBC) interface problem, subclass's virtual functions may get accidentally invoked when base class implementation changes without notice. For example, the following code snippet (inspired by ) uses the NVI idiom to impl...
Thread-Safe Interface, from Pattern-Oriented Software Architecture (volume 2) by Douglas Schmidt et al.Selective Open Recursion: Modular Reasoning about Components and Inheritance - Jonathan Aldrich, Kevin Donnelly. Virtuality!-- Herb Sutter Conversations: Virtually Yours-- Jim Hyslop and Herb Sutter Should I use protected virtuals instead of public virtuals?-- Marshall Cline
Aug 16, 2016 · I have read many Q&As about when (and when not) to use a virtual destructor, but I am stumped by this sample code. My textbook understanding of C++ says: "Aha! A base class without a virtual destructor is bad. Memory leak or undefined behaviour may occur."
May 7, 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.
The non-virtual interface pattern is a design pattern that controls how methods in a base class are overridden. Base classes include public, non-virtual members that may be called by clients and a set of overridable methods containing core functionality.
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What is a non-virtual interface pattern?
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Is a Class A virtual destructor?
Nov 7, 2019 · By default, methods are non-virtual, and they cannot be overridden. Virtual modifiers cannot be used with static, abstract, private, and override modifiers. Let's demonstrate this with a code example.
