Static keyword in class definitions

The second way is by having a variable or function in a class being defined as static. Normally, when you create an instance of a class, the compiler has to set aside additional memory for each variable that is contained inside of the class in consecutive blocks of memory. When we declare something as static, instead of creating a new variable to hold data, a single variable is shared by all of the instances of the class. In addition, since it's shared by all of the copies, you don't need to have an instance of the class to call it. Take a look at the following bolded code to create our variable:

class StaticExamples 
 
{ 
public: 
  static float classVariable;
  static void StaticFunction() 
  { 
    // Note, can only use static variables and functions within 
    // static function 
    std::string toDisplay = "\n I can be called anywhere!
    classVariable value: " + std::to_string(classVariable); 
 
    printf(toDisplay.c_str()); 
  } 
 
  void InFunction() 
  { 
    static int enemyCount = 0; 
 
    // Increase the value of enemyCount 
    enemyCount += 10; 
 
    std::string toDisplay = "\n Value of enemyCount:  " +  
                std::to_string(enemyCount); 
 
    printf(toDisplay.c_str()); 
  } 
};

Now, in the preceding code we define a variable and a function, but this isn't all the prep work we need to do. When creating a static variable, you cannot initialize it from within the class, and instead need to do it in a .cpp file instead of the .h file we could use for the class definition. You'll get errors if you do not initialize it, so it's a good idea to do that. In our case, it'd look like the following:

// StaticExamples.cpp 
float StaticExamples::classVariable = 2.5f;

Note that, when we initialize, we also need to include the type, but we use the ClassName::variableName template similar to how you define functions in .cpp files. Now that everything's set up, let's see how we can access them inside our normal code:

StaticExamples::StaticFunction(); 
StaticExamples::classVariable = 5; 
StaticExamples::StaticFunction();

Note that instead of accessing it via creating a variable, we can instead just use the class name followed by the scope operator (::) and then select which static variable or function we'd like to use. When we run it, it'll look like this:

As you can see, it works perfectly!