Defining member functions inside or outside the class in C++

The member functions of a class can be defined in two ways:-

Inside the class
Outside the class

Defining member functions inside the class in C++

This is the most common way of defining members functions of a class.

In this case we define member functions of a class in the same manner as we define normal functions.

Functions defined inside a class are automatically inline. Normally data members of a class are defined as private and member functions of a class are defined as public members of a class.

Example:

using namespace std;
class student
{
public:
   //Member function inside the class
  void display() 
  {
  cout<<”Inside the class”;
  }
};

int main()()
{
 student obj;
 obj.display();
 return 0;
}

Defining member functions outside the class  in C++

We can also define member functions outside a class. There are two steps involved in defining member function outside the class.

Declaration of member function
Member Function definition

Declaration of member function

We need to declare the member functions inside the class but the function body is created outside the class.

Syntax to declare a member function as:

class <class_name>
{
 visibility mode:
   member function();
}

Example:

class student
{
  public:
    void display(); //Member function Declaration 
};

Member Function definition

After declaring member function inside the class, we need to define its body outside the class.

Syntax:

Return-type class_name::function name(Agument_list)
{
 function-body
}

Return-type refers to the return type of member function.
Class_name is the name of class in which member function is declared.
Argument_list is the list of various formal arguments passed to the function.
Function-body contains the valid statements of C++ which will be executed as a part of the function.

Example:

using namespace std;
class student
{
public:
   //Member function declaration inside the class
  void display(); 
 };
 //Member function definition outside the class
void student::display()  
{  
   cout<<”Outside the class”;  
}

int main()()
{
 student obj;
 obj.display();
 return 0;
}

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Lesson tags: Defining member function outside a class in C++, Defining member functions inside a class in C++

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