C++ - Static Member Function

Static Member Function

Static Member Function in C++ is a special kind of function that belongs to the class itself rather than any specific object. A static keyword is used to define those functions. They can be directly called by using just the class name, without creating an instance of the class, which is an object.

These are only accessible within the body of the class they are defined in, thus, implementing class-wide operations and certain security measures.

Syntax

Here is the given syntax for static member functions in C++:

class ClassName {
   public:
      static returnType functionName(parameters) {
         // Function body
      }
};

Example of Static Member Function

Here is the following example for the static member function:

#include <iostream>
using namespace std;

class MyClass {
   public:
      static void displayMessage() {
         cout << "Hello, World!";
      }
};

int main() {
   // Calling static member function
   MyClass::displayMessage();

   return 0;
}

Output

Hello, World!

Explanation

• We define a class MyClass with a public static member function displayMessage().
• The function simply prints “Hello, World!”.
• In the main function, we directly call the function using the class name. Observe we haven’t created an instance of the class to call the function.

Key features of Static Member Functions

• There's no access to this pointer with static functions as they're not tied to an object instance.
• These functions can be invoked using a class name.
• They can only work with static members or other static functions of the class.

When should static member functions be used?

These are best suited for tasks that involve shared data and logic which is unrelated to specific objects. Here are some scenarios −

• Maintaining counters, and handling global configurations.
• In implementing interface methods that don't require an object state.
• Utility or helper functions like mathematical operations, data validations, etc.

Example

#include <iostream>
using namespace std;
class MathOperation {
   public:
      static int square(int num) {
         return num * num;
      }
};

int main() {
   std::cout << "Square of 2: " << MathOperation::square(2) << '\n';
   return 0;
}

Output

Square of 2: 4