C++ 中友元函数的优缺点

2024 年 8 月 28 日 | 3 分钟阅读

我们创建友元函数是为了在 C++ 面向对象编程系统中访问不同的修饰符，例如 Protected、Private 和 Public。友元函数或友元类通常在类的外部定义，但仍然可以访问类代码中定义的类的私有（private）、保护（protected）和公共（public）成员。

优点	缺点
声明可以放在代码的任何位置	它不会被传递给派生类
调用它时无需创建对象。	它们没有存储指定类。
也可以使用友元函数访问类的非公有成员。	当多个类关联在一起时，友元函数非常有用。
它可以添加额外的功能。	允许将私有和保护成员显示为类的信息。
使编程体验比以往任何时候都更高效。	它可以在其定义的同一个类中同时拥有公有和私有保护成员。

C++ 代码

// below, we are writing down the C++ programming language code to 
// demonstrate the concept of Advantage and disadvantage friend function C++
// which depicts how the friend function can act as a bridge between classes
#include<iostream>
using namespace std;


// the below class declaration is a forward declaration
class JTP;
class XYZ
{
	int x;
	public:
		void set_data(int a)
		{
			x=a;
		}
		
		friend void max(XYZ, JTP);
};


class JTP {
	int y;
	public:
		void set_data(int a)
		{
			y=a;
		}	
		
	friend void max(XYZ, JTP);
};

void max(XYZ t1,JTP t2)
{
	if(t1.x>t2.y)
		cout<<t1.x;
	else
		cout<<t2.y;
}

// the driver code functionality starts from here
int main()
{
	JTP _abc;
	XYZ _xyz;
	_xyz.set_data(120);
	_abc.set_data(3135);
	
	// the below code snippet helps us with calling down the friend
	// function which we have declared to perform operations
	max(_xyz,_abc); 
	return 0;
}

输出

/tmp /mB gjSey FC Z.o
3135

C++ 代码

// below, we are writing down the C++ programming language code to 
// demonstrate the concept of Advantage and disadvantage friend function C++
// which depicts how the friend function can act as a bridge between classes
#include<iostream>
using namespace std;

// defining class A from here
class A
{
	int x;
		public:
			
	A()
	{
		x=3979;
	}
	// the below small code snippet is enough to define the 
	// friend class for our code to demonstrate the usage of class B
	friend class B; 
};
// defining class B from here
class B
{
	public:
		void display(A &t)
		{
			cout<<endl<<"After performing the operations the value for X we have got as: "<<t.x;
		}
};

// the driver code functionality starts from here
main()
{
	A _a;
	B _b;
	_b.display(_a);
	return 0;
}

输出

/tmp /mB gjSey FC Z.o
After performing the operations, the value for X we have got is 3979

C++ 代码

// below, we are writing down the C++ programming language code to 
// demonstrate the concept of Advantage and disadvantage friend function C++
// which depicts how the friend function can act as a bridge between classes
// and to find the largest of two numbers using the friend function method

#include<iostream>
using namespace std;

class Largest
{
    // declaring the variables a,b and m for performing the operations
	int a,b,m;
	public:
		void set_data();
		friend void find_max(Largest);	
};

// writing the void function to take the inputs from the user without 
// writing them again and again from the int main function
void Largest::set_data()
{
    // string display to ask the user to give the input
	cout<<"Dear User, please enter the value for the variable first no: ";
	cin>>a;
	cout<<"Dear User, please enter the value for the variable second no: ";
	cin>>b;
}


// function, which calculates the largest among the inputs entered by the 
// user
void find_max(Largest t)
{
	if(t.a>t.b)
		t.m=t.a;
	else
		t.m=t.b;
		
		Cout <<"Hey! User, the maximum number among the inputs entered by you is: "<<t.m;
}

// the driver code functionality starts from here
main()
{
	Largest l;
	l.set_data();
	find_max(l);
	return 0;
}

输出

/tmp /mB gjSey FC Z.o
Dear User, please enter the value for the variable first no: 35
Dear User, please enter the value for the variable second no: 365
Hey! User, the maximum number among the inputs entered by you is: 365

下一个主题C++ 预处理器

C++ 中友元函数的优缺点

联系信息

关注我们

教程

面试题

在线编译器

Python

Java

.Net Framework

AI, ML and Data Science

Cloud Technology

B.Tech and MCA

Web Technology

PHP

Software Testing

Technical Interview

Java Interview

Python

Web Interview

Database Interview

B.Tech / MCA

Important Interview

Software Testing Interview

Company Interviews

Online Compilers

Multiple Choice Questions

C++ 教程

C++ 控制语句

C++ 函数

C++ 数组

C++ 类和对象

C++ 构造函数

C++ 继承

C++ 多态

C++ 抽象

C++ 命名空间

C++ 模板

C++ 字符串

C++ 指针

信号处理

C++ 异常

C++ 文件与流

C++ STL 教程

面试题

选择题

C++ 程序

C++ STL Stack

C++ STL Bitset

C++ STL Deque

C++ STL List

C++ STL Map

C++ STL Math

C++ STL priority_queue

C++ STL Queue

C++ STL Multiset

C++ STL Multimap

C++ STL Set

C++ STD Strings

C++ STL Vector

C++ 操纵符

C++ STL Algorithms

C++ Algorithm

C++ Iterators

C++ 杂项

C++ 中友元函数的优缺点

相关帖子

C++ 和 Java 中捕获基类和派生类异常

C/C++ Iswspace() 函数

C++ Falcon

C++ Isdigit() 函数

悬空、空、NULL 和野指针

C++ String_view

C++ 位掩码

C++ 反转数字程序

C++ wmemmove() 函数

C++ 面向对象的好处

订阅 Tpoint Tech

联系信息

关注我们

教程

面试题

在线编译器