Easy tutorial for C / C ++ - class 3 (Constructor)

Easy tutorial for C / C ++ - class 3 (Constructor)

Constructor :

- Initialization of an object usually means initialization of member variables. Commonly member variables are set to 'private', you need to change the access specifier to 'public' or define the initialization function separately to initialize it arbitrarily.

- A special function provided to compensate for this is the Constructor. A constructor is a special member function for initializing an object. It has the same name as the class name and does not specify the data type of the return value. You can also overload with different arguments.

- If the programmer does not define a constructor, the C ++ compiler automatically creates a default constructor. It is equivalent to a class name, and has no role as an argumentless constructor.

- Let's look at an example.

Example Code

#include <iostream>

#include <iomanip>

using namespace std;

class tClass{

   private :

     int Na;

     int Nb;

   public :

     tClass();

     tClass(int, int);

     void prn();

};

tClass::tClass(){

    Na = 10;

    Nb = 20;

}

tClass::tClass(int A, int B){

    Na = A;

    Nb = B;

}

void tClass::prn(){

     cout << " Na = " << Na << ", Nb = " << Nb << endl ;

}

int main() {

     tClass x;

     cout << " Class x " << endl ;

     x.prn();

     cout << endl ;

     tClass y(50,60);

     cout << " Class y " << endl ;

     y.prn();

     return 0;

}

- We created the class 'tClass' and declared the member variables 'Na, Nb'. We created a constructor 'tClass ()' with no arguments and a constructor 'tClass (int, int)' with two integer arguments.

- Constructor 'tClass ()' is a constructor that initializes the member variables Na and Nb to 10 and 20, respectively. The constructor 'tClass (int, int)' allows the user to set the initial values of the member variables Na and Nb when creating the object.

- First we declare the object 'x' in the main function and print the value of the member variables. Let 's declare object' y 'and give parentheses' ()' to input values 50 and 60. In this case, a constructor with two integer arguments is called and the given value is assigned to each member variable. Let's call the function 'prn ()' to check the result.

results :

 Class x

 Na = 10, Nb = 20

 Class y

 Na = 50, Nb = 60

- For object 'x', a constructor with no arguments is called and the result is 10 and 20 for Na and Nb, respectively. If you call the output function 'prn ()', you will see that 10 and 20 are output.

- When declaring object 'y', we gave two arguments 50 and 60. At that time, a constructor with two arguments is called, and 50 and 60 are assigned to each member variable. When you call the output function 'prn ()', you will see that 50 and 60 are output.