override specifier (since C++11)

 

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override specifier(C++11)

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Specifies that a virtual function overrides another virtual function.

Syntax

The identifier override, if used, appears immediately after the declarator in the syntax of a member function declaration or a member function definition inside a class definition.

declaratorvirt-specifier-seq (optional)pure-specifier (optional)	(1)
declaratorvirt-specifier-seq (optional)function-body	(2)

1) In a member function declaration, override may appear in virt-specifier-seq immediately after the declarator, and before the pure-specifier, if used.

2) In a member function definition inside a class definition, override may appear in virt-specifier-seq immediately after the declarator and just before function-body.

In both cases, virt-specifier-seq, if used, is either override or final, or final override or override final.

Explanation

In a member function declaration or definition, override specifier ensures that the function is virtual and is overriding a virtual function from a base class. The program is ill-formed (a compile-time error is generated) if this is not true.

override is an identifier with a special meaning when used after member function declarators; it is not a reserved keyword otherwise.

Keywords

override

Example

Run this code

#include <iostream>   struct A {virtualvoid foo();void bar();virtual ~A();};   // member functions definitions of struct A:void A::foo(){std::cout<<"A::foo();\n";} A::~A(){std::cout<<"A::~A();\n";}   struct B : A {// void foo() const override; // Error: B::foo does not override A::foo// (signature mismatch)void foo() override;// OK: B::foo overrides A::foo// void bar() override; // Error: A::bar is not virtual ~B() override;// OK: `override` can also be applied to virtual// special member functions, e.g. destructorsvoid override();// OK, member function name, not a reserved keyword};   // member functions definitions of struct B:void B::foo(){std::cout<<"B::foo();\n";} B::~B(){std::cout<<"B::~B();\n";}void B::override(){std::cout<<"B::override();\n";}   int main(){ B b; b.foo(); b.override();// OK, invokes the member function `override()`int override{42};// OK, defines an integer variablestd::cout<<"override: "<< override <<'\n';}

Output:

B::foo(); B::override(); override: 42 B::~B(); A::~A();

See also

final specifier(C++11)

declares that a method cannot be overridden or a class be derived from