C++ Function Overriding用法及代码示例

A Functions是一个语句块，它们通过接受一些输入并产生特定的输出来共同执行特定的任务。C++ 中的函数重写被称为在其派生类中以相同的签名(即返回类型和参数)重新定义基类函数。它属于以下类别运行时多态性。

Real-Life 函数重写示例

这个概念最好的Real-life例子是印度宪法。印度借鉴了政府机构的政治准则、结构、程序、权力和义务，规定了其他国家公民的基本权利、指导原则和义务，并自行实施；使其成为世界上最大的宪法。

另一个发展real-life 的例子可能是 RBI(印度储备银行)与其他国有银行(如 SBI、PNB、ICICI 等)之间的关系。其中 RBI 行使相同的监管职能，其他银行则按原样遵循。

Real-Life Example of Function Overriding

函数重写

用法:

class Parent{

  access_modifier:

    // overridden function

    return_type name_of_the_function(){}

  };

}

  class child : public Parent {

    access_modifier:

      // overriding function

      return_type name_of_the_function(){}

    };

  }

例子：

C++


// C++ program to demonstrate function overriding
#include <iostream>
using namespace std;
class Parent {
public:
    void GeeksforGeeks_Print()
    {
        cout << "Base Function" << endl;
    }
};
class Child : public Parent {
public:
    void GeeksforGeeks_Print()
    {
        cout << "Derived Function" << endl;
    }
};
int main()
{
    Child Child_Derived;
    Child_Derived.GeeksforGeeks_Print();
    return 0;
}

输出

Derived Function

函数重写的变化

1.从派生类调用重写函数

C++


// C++ program to demonstrate function overriding
// by calling the overridden function
// of a member function from the child class
#include <iostream>
using namespace std;
class Parent {
public:
    void GeeksforGeeks_Print()
    {
        cout << "Base Function" << endl;
    }
};
class Child : public Parent {
public:
    void GeeksforGeeks_Print()
    {
        cout << "Derived Function" << endl;
        // call of overridden function
        Parent::GeeksforGeeks_Print();
    }
};
int main()
{
    Child Child_Derived;
    Child_Derived.GeeksforGeeks_Print();
    return 0;
}

输出

Derived Function
Base Function

Call Overridden Function From Derived Class

的输出从派生类调用重写函数

2. 使用指针调用重写函数

C++


// C++ program to access overridden function using pointer
// of Base type that points to an object of Derived class
#include <iostream>
using namespace std;
class Parent {
public:
    void GeeksforGeeks()
    {
        cout << "Base Function" << endl;
    }
};
class Child : public Parent {
public:
    void GeeksforGeeks()
    {
        cout << "Derived Function" << endl;
    }
};
int main()
{
    Child Child_Derived;
    // pointer of Parent type that points to derived1
    Parent* ptr = &Child_Derived;
    // call function of Base class using ptr
    ptr->GeeksforGeeks();
    return 0;
}

输出

Base Function

3. 重写函数对基类的访问

C++


// C++ program to access overridden function
// in main() using the scope resolution operator ::
#include <iostream>
using namespace std;
class Parent {
public:
    void GeeksforGeeks()
    {
        cout << "Base Function" << endl;
    }
};
class Child : public Parent {
public:
    void GeeksforGeeks()
    {
        cout << "Derived Function" << endl;
    }
};
int main()
{
     Child Child_Derived;
     Child_Derived.GeeksforGeeks();
    // access GeeksforGeeks() function of the Base class
     Child_Derived.Parent::GeeksforGeeks();
    return 0;
}

输出

Derived Function
Base Function

Access of Overridden Function to the Base Class

重写函数对基类的访问

4. 访问重写函数

C++


// C++ Program Demonstrating
// Accessing of Overridden Function
#include <iostream>
using namespace std;
// defining of the Parent class
class Parent
{
public:
    // defining the overridden function
    void GeeksforGeeks_Print()
    {
        cout << "I am the Parent class function" << endl;
    }
};
// defining of the derived class
class Child : public Parent
{
public:
    // defining of the overriding function
    void GeeksforGeeks_Print()
    {
        cout << "I am the Child class function" << endl;
    }
};
int main()
{
    // create instances of the derived class
    Child GFG1, GFG2;
    // call the overriding function
    GFG1.GeeksforGeeks_Print();
    // call the overridden function of the Base class
    GFG2.Parent::GeeksforGeeks_Print();
    return 0;
}

输出

I am the Child class function
I am the Parent class function

函数重载与函数重写

Function Overloading	Function Overriding
它属于编译时多态性	它属于运行时多态性
一个函数可以被重载多次，因为它是在编译时解析的	函数不能被重写多次，因为它是在运行时解析的
无需继承即可执行	没有继承就无法执行
他们在同一个范围内	它们的范围不同。

要了解更多信息，您可以参考 函数重载 VS 函数重写.

相关用法

注：本文由纯净天空筛选整理自harsh_shokeen大神的英文原创作品 Function Overriding in C++。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。