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我可以调用基类's virtual function if I' m覆盖它吗？

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295

假设我有类 Foo 和 Bar 设置如下：

class Foo
{
public:
    int x;

    virtual void printStuff()
    {
        std::cout << x << std::endl;
    }
};

class Bar : public Foo
{
public:
    int y;

    void printStuff()
    {
        // I would like to call Foo.printStuff() here...
        std::cout << y << std::endl;
    }
};

正如在代码中注释的那样，我'd like to be able to call the base class'的函数是'm overriding. In Java there'的 super.funcname() 语法 . 这可能在C？

c++ virtual-functions override

7 回答

  • 0

    如果要从派生类中调用基类函数，只需在提及基类名称（如 Foo::printStuff() ）的情况下调用重写函数 .

    代码在这里

    #include <iostream>
using namespace std;

class Foo
{
public:
    int x;

    virtual void printStuff()
    {
         cout<<"Base Foo printStuff called"<<endl;
    }
};

class Bar : public Foo
{
public:
    int y;

    void printStuff()
    {
        cout<<"derived Bar printStuff called"<<endl;
        Foo::printStuff();/////also called the base class method
    }
};

int main()
{
    Bar *b=new Bar;
    b->printStuff();
}

    同样，您可以在运行时确定使用该类的对象（派生或基础）调用哪个函数 . 但这要求您在基类中的函数必须标记为虚拟 .

    代码如下

    #include <iostream>
using namespace std;

class Foo
{
public:
    int x;

    virtual void printStuff()
    {
         cout<<"Base Foo printStuff called"<<endl;
    }
};

class Bar : public Foo
{
public:
    int y;

    void printStuff()
    {
        cout<<"derived Bar printStuff called"<<endl;
    }
};

int main()
{

    Foo *foo=new Foo;
    foo->printStuff();/////this call the base function
    foo=new Bar;
    foo->printStuff();
}
    回复于
  • 0

    C语法是这样的：

    class Bar : public Foo {
  // ...

  void printStuff() {
    Foo::printStuff(); // calls base class' function
  }
};
    回复于
  • 6

    是，

    class Bar : public Foo
{
    ...

    void printStuff()
    {
        Foo::printStuff();
    }
};

    它与Java中的 super 相同，只是它允许在具有多个继承时从不同的基础调用实现 .

    class Foo {
public:
    virtual void foo() {
        ...
    }
};

class Baz {
public:
    virtual void foo() {
        ...
    }
};

class Bar : public Foo, public Baz {
public:
    virtual void foo() {
        // Choose one, or even call both if you need to.
        Foo::foo();
        Baz::foo();
    }
};
    回复于
  • 108

    有时你需要调用基类的实现，当你不在派生函数中时...它仍然有效：

    struct Base
{
    virtual int Foo()
    {
        return -1;
    }
};

struct Derived : public Base
{
    virtual int Foo()
    {
        return -2;
    }
};

int main(int argc, char* argv[])
{
    Base *x = new Derived;

    ASSERT(-2 == x->Foo());

    //syntax is trippy but it works
    ASSERT(-1 == x->Base::Foo());

    return 0;
}
    回复于
  • 63

    为了防止你为你班上的很多功能做到这一点：

    class Foo {
public:
  virtual void f1() {
    // ...
  }
  virtual void f2() {
    // ...
  }
  //...
};

class Bar : public Foo {
private:
  typedef Foo super;
public:
  void f1() {
    super::f1();
  }
};

    如果要重命名Foo，这可能会节省一些写入 .

    回复于
  • 390

    检查一下......

    #include <stdio.h>

class Base {
public:
   virtual void gogo(int a) { printf(" Base :: gogo (int) \n"); };    
   virtual void gogo1(int a) { printf(" Base :: gogo1 (int) \n"); };
   void gogo2(int a) { printf(" Base :: gogo2 (int) \n"); };    
   void gogo3(int a) { printf(" Base :: gogo3 (int) \n"); };
};

class Derived : protected Base {
public:
   virtual void gogo(int a) { printf(" Derived :: gogo (int) \n"); };
   void gogo1(int a) { printf(" Derived :: gogo1 (int) \n"); };
   virtual void gogo2(int a) { printf(" Derived :: gogo2 (int) \n"); };
   void gogo3(int a) { printf(" Derived :: gogo3 (int) \n"); };       
};

int main() {
   std::cout << "Derived" << std::endl;
   auto obj = new Derived ;
   obj->gogo(7);
   obj->gogo1(7);
   obj->gogo2(7);
   obj->gogo3(7);
   std::cout << "Base" << std::endl;
   auto base = (Base*)obj;
   base->gogo(7);
   base->gogo1(7);
   base->gogo2(7);
   base->gogo3(7);

   std::string s;
   std::cout << "press any key to exit" << std::endl;
   std::cin >> s;
   return 0;
}

    产量

    Derived
 Derived :: gogo (int)
 Derived :: gogo1 (int)
 Derived :: gogo2 (int)
 Derived :: gogo3 (int)
Base
 Derived :: gogo (int)
 Derived :: gogo1 (int)
 Base :: gogo2 (int)
 Base :: gogo3 (int)
press any key to exit

    最好的方法是使用 base::function ，如@sth

    回复于
  • 27

    是的，你可以打电话给它 . 用于在子类中调用父类函数的C语法是

    class child: public parent {
  // ...

  void methodName() {
    parent::methodName(); // calls Parent class' function
  }
};

    阅读有关函数overriding的更多信息 .

    回复于

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