c ++查找字符串

Program 1:

程序1：

#include <iostream>
using namespace std;
class Sample {
int A, B;
friend void fun();
};
void fun()
{
Sample S;
S.A = 10;
S.B = 20;
cout << S.A << " " << S.B << endl;
}
int main()
{
fun();
return 0;
}

Output:

输出：

10 20

Explanation:

说明：

Here, we created a class Sample that contains private data members A and B.

在这里，我们创建了一个类Sample ，其中包含私有数据成员A和B。

As we know that, we cannot access the private members outside the class. Here, we defined a non-member function as a friend function that can access private members.

众所周知，我们无法访问课程之外的私人成员。 在这里，我们将非成员函数定义为可以访问私有成员的朋友函数。

Then, we set the values into A and B and printed.

然后，将值设置为A和B并打印。

Program 2:

程式2：

#include <iostream>
using namespace std;
class Sample {
int A, B;
void fun();
};
friend void fun()
{
Sample S;
S.A = 10;
S.B = 20;
cout << S.A << " " << S.B << endl;
}
int main()
{
fun();
return 0;
}

Output:

输出：

main.cpp:9:1: error: ‘friend’ used outside of class
friend void fun()
^~~~~~
main.cpp: In function ‘void fun()’:
main.cpp:13:7: error: ‘int Sample::A’ is private within this context
S.A = 10;
^
main.cpp:5:9: note: declared private here
int A, B;
^
main.cpp:14:7: error: ‘int Sample::B’ is private within this context
S.B = 20;
^
main.cpp:5:12: note: declared private here
int A, B;
^
main.cpp:16:15: error: ‘int Sample::A’ is private within this context
cout << S.A << " " << S.B << endl;
^
main.cpp:5:9: note: declared private here
int A, B;
^
main.cpp:16:29: error: ‘int Sample::B’ is private within this context
cout << S.A << " " << S.B << endl;
^
main.cpp:5:12: note: declared private here
int A, B;
^

Explanation:

说明：

This code will generate an error because we are accessing the private members of class Sample in the function fun() but did not define fun() as a friend within the class. We need to define fun() as a friend inside the class.

该代码将产生错误，因为我们正在访问fun()函数中的Sample类的私有成员，但未将fun()定义为该类中的朋友 。 我们需要将fun()定义为类中的朋友。

class Sample
{
int A,B;
friend void fun();
};

Program 3:

程式3：

#include <iostream>
using namespace std;
class Sample {
int A, B;
friend void fun();
};
friend void fun()
{
Sample S;
S.A = 10;
S.B = 20;
cout << S.A << " " << S.B << endl;
}
int main()
{
fun();
return 0;
}

Output:

输出：

main.cpp:9:1: error: ‘friend’ used outside of class
friend void fun()
^~~~~~

Explanation:

说明：

This code will generate an error because we used friend keyword in the definition of the function fun(). We cannot use a friend keyword outside the class.

该代码将产生错误，因为我们在函数fun()的定义中使用了friend关键字。 我们不能在课程外使用friend关键字。

Program 4:

计划4：

#include <iostream>
using namespace std;
class Sample1 {
int A, B;
public:
friend class Sample2;
};
class Sample2 {
int X, Y;
void fun1()
{
Sample1 S;
S.A = 10;
S.B = 20;
cout << S.A << " " << S.B << endl;
}
};
int main()
{
Sample2 S;
S.fun1();
return 0;
}

Output:

输出：

main.cpp: In function ‘int main()’:
main.cpp:27:12: error: ‘void Sample2::fun1()’ is private within this context
S.fun1();
^
main.cpp:14:10: note: declared private here
void fun1()
^~~~

Explanation:

说明：

This code will generate an error, we are accessing the private member function fun1() in the main() function.

此代码将产生错误，我们正在访问main()函数中的私有成员函数fun1() 。

翻译自: https://www.includehelp.com/cpp-tutorial/friend-function-find-output-programs-set-1.aspx

c ++查找字符串