zoukankan      html  css  js  c++  java
  • final specifier (since C++11)

    Specifies that a virtual function cannot be overridden in a derived class or that a class cannot be inherited from.

    Syntax

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

    declarator virt-specifier-seq(optional) pure-specifier(optional) (1)  
     
    declarator virt-specifier-seq(optional) function-body (2)  
     
    class-key attr(optional) class-head-name class-virt-specifier(optional) :base-specifier-list(optional) (3)  
     
    1) In a member function declaration, final may appear in virt-specifier-seq immediately after the declarator, and before the pure-specifier, if used.
    2) In a member function definition, final may appear in virt-specifier-seq immediately after the declarator and just before function-body (which may begin with a member initializer list)
    3) In a class definition, final may appear as class-virt-specifier immediately after the name of the class, just before the colon that begins the base-specifier-list, if used.

    In the cases (1,2), virt-specifier-seq, if used, is either override or final, or final override or override final. In the case (3), the only allowed value of class-virt-specifier, if used, is final

    Explanation

    When used in a virtual function declaration or definition, final ensures that the function is virtual and specifies that it may not be overridden by derived classes. The program is ill-formed (a compile-time error is generated) otherwise.

    When used in a class definition, final specifies that this class may not appear in the base-specifier-list of another class definition (in other words, cannot be derived from). The program is ill-formed (a compile-time error is generated) otherwise. final can also be used with a union definition, in which case it has no effect (other than on the outcome ofstd::is_final), since unions cannot be derived from)

    final is an identifier with a special meaning when used in a member function declaration or class head. In other contexts it is not reserved and may be used to name objects and functions.

    Example

    struct Base
    {
        virtual void foo();
    };
     
    struct A : Base
    {
        virtual void foo() final; // A::foo is final
        void bar() final; // Error: non-virtual function cannot be final
    };
     
    struct B final : A // struct B is final
    {
        void foo(); // Error: foo cannot be overridden as it's final in A
    };
     
    struct C : B // Error: B is final
    {
    };

    See also

  • 相关阅读:
    MPI编程简述
    网购时代,写在消费者权益保护的新篇章大企业
    在哪里?
    H264 编解码器架构简单
    Unity+NGUI打造网络图片异步加载和本地缓存工具(一)
    分数减法
    JAVA设计模式(09):结构化-代理模式(Proxy)
    I2C驱动程序框架probe道路
    安卓表格布局android:collapseColumns,android:shrinkColumns和stretchColumn
    智课雅思词汇---七、cur是什么意思
  • 原文地址:https://www.cnblogs.com/scarecrow-blog/p/5799946.html
Copyright © 2011-2022 走看看