Specifies that avirtual function overrides another virtual function.
The identifieroverride, if used, appears immediately after thedeclarator in the syntax of a member function declaration or a member function definition inside a class definition.
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| declaratorvirt-specifier-seq (optional)pure-specifier (optional) | (1) | |
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| declaratorvirt-specifier-seq (optional)function-body | (2) | |
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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 invirt-specifier-seq immediately after the declarator and just beforefunction-body.
In both cases,virt-specifier-seq, if used, is eitheroverride orfinal, orfinal override oroverride final.
[edit]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 anidentifier with a special meaning when used after member function declarators; it is not a reservedkeyword otherwise.
[edit]Keywords
override
[edit]Example
#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: 42B::~B();A::~A();
[edit]See also
