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Member Functions in C++

1. Nested Member Functions

A nested member function is a function defined inside another member function. However, in C++, direct nesting of functions is not allowed. You can call another member function within a member function, which is sometimes referred to as nesting.

class Example {
public:
    void func1() {
        func2(); // Calling another member function
    }

    void func2() {
        // Some code
    }
};
                    

2. Overloaded Member Functions

Overloading allows multiple functions with the same name but different parameters. It helps in defining similar operations with different types of data.

class Example {
public:
    void display(int i) {
        std::cout << "Integer: " << i << std::endl;
    }

    void display(double d) {
        std::cout << "Double: " << d << std::endl;
    }
};
                    

3. Constant Member Functions

Constant member functions do not modify any data members of the class. They are declared using the const keyword.

class Example {
private:
    int data;
public:
    int getData() const {
        return data; // This function doesn't modify any data members
    }
};
                    

4. Default Member Functions

Default member functions are automatically provided by the compiler if not explicitly defined. These include the default constructor, destructor, copy constructor, and assignment operator.

class Example {
public:
    Example() = default; // Default constructor
};
                    

5. Inline Member Functions

Inline member functions are defined inside the class definition and are expanded in line where they are called. They can improve performance by avoiding function call overhead.

class Example {
public:
    inline int add(int a, int b) {
        return a + b;
    }
};
                    

6. Static Member Functions

Static member functions are shared among all objects of a class and can be called without an instance of the class.

class Example {
public:
    static void showMessage() {
        std::cout << "Hello from static function!" << std::endl;
    }
};
                    

Types of Data Members in C++

1. Constant Data Members

Constant data members are read-only and must be initialized at the time of declaration or within the constructor initializer list.

class Example {
private:
    const int constantData;
public:
    Example(int value) : constantData(value) {}
};
                    

2. Mutable Data Members

Mutable data members can be modified even within a constant member function. They provide a way to alter certain data members without affecting the const nature of the function.

class Example {
private:
    mutable int mutableData;
public:
    void modify() const {
        mutableData = 10; // Allowed even in const function
    }
};
                    

3. Static Data Members

Static data members are shared among all objects of a class. They are declared within the class but must be defined outside the class.

class Example {
public:
    static int staticData;
};

int Example::staticData = 0; // Definition outside the class