C ++纯虚函数有体 [英] C++ pure virtual function have body

问题描述

纯虚函数（当我们设置 = 0 时）也可以有一个函数体。

Pure virtual functions (when we set = 0) can also have a function body.

推荐答案

你的假设是：纯虚函数不能被调用是绝对不正确的。当一个函数被声明为纯虚函数时，它只是意味着这个函数不能通过虚拟调度机制动态调用。然而，这个非常相同的函数可以容易地被静态地调用 ，而没有虚拟分派。

Your assumption that pure virtual function cannot be called is absolutely incorrect. When a function is declared pure virtual, it simply means that this function cannot get called dynamically, through a virtual dispatch mechanism. Yet, this very same function can easily be called statically, without virtual dispatch.

在C ++语言中当在调用中使用函数的限定名时，即在调用中指定的函数名具有< class name> ::< function name> form。

In C++ language static call to a virtual function is performed when a qualified name of the function is used in the call, i.e. when the function name specified in the call has the <class name>::<function name> form.

$ b

For example

struct S {
  virtual void foo() = 0;
};

void S::foo() {
  // body for the pure virtual function `S::foo`
}

struct D : S {
  void foo() {
    S::foo(); // static call to `S::foo` from derived class
  }
};

int main() {
  D d;
  d.S::foo(); // another static call to `S::foo`
}

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