What is the difference between C++ static functions and friend functions?

Static functions are class methods that only access static members and do not receive this pointers; friend functions do not belong to the class and can access all members and receive this pointers.

The difference between static functions and friend functions in C

Static functions

• Belongs to a class but does not belong to any specific object. It can also be called a class method.
• Declared using the static keyword.
• Only static members of the class can be accessed.
• will not receive the this pointer.

Friend function

• Does not belong to any class.
• Use the friend keyword statement.
• Can access all members of the class, including private members.
• can receive this pointer.

Table summary

##Class membershipisNotAccess rightsClass static membersAll members of the classthis pointerNot acceptedCan be receivedDeclaration method

Features	Static function	Friend functions
	static Keyword	friend Keywords

Practical case

Static function example: Calculate circle Area

class Circle {
public:
    static double calculateArea(double radius) {
        return 3.14 * radius * radius;
    }
};

int main() {
    double radius = 5.0;
    double area = Circle::calculateArea(radius);
    cout << "圆的面积：" << area << endl;
    return 0;
}

Friend function example:Print the value of private member

class Student {
private:
    int age;

public:
    friend void printAge(Student& student);
};

void printAge(Student& student) {
    cout << "年龄：" << student.age << endl;
}

int main() {
    Student student;
    student.age = 20;
    printAge(student);
    return 0;
}

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