In c++::how to use

In C, the :: operator is used to access static members or global variables of a class. It lets you access static members even without a class instance, and global variables even without a source file.

:: Usage in C

:: is a operator, called the domain resolution operator. It is used to access static members and global variables of a class.

Accessing static members of a class

Static members belong to the class rather than the class instance. You can use the :: operator to access static members of a class even if there is no instance of the class.

<code class="cpp">class MyClass {
public:
    static int numInstances;
};

int main() {
    // 访问静态成员
    cout << MyClass::numInstances << endl;
    return 0;
}</code>

Accessing global variables

Global variables are available in all code files. You can use the :: operator to access global variables even if there is no source file in which they are defined.

<code class="cpp">// 定义全局变量
int globalVar = 10;

// 在另一个文件中访问全局变量
int main() {
    cout << ::globalVar << endl;
    return 0;
}</code>

Note:

• :: must follow the class name or variable name, and there must be no spaces in the middle.
• In the same file, when accessing static members or global variables, you usually do not need to use the :: operator.
• You need to use the :: operator only when you need to access private static members or global variables in different files or from code.

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