Page 130 - DCAP404 _Object Oriented Programming

Unit 6: Constructors and Destructors

{ Notes
char * FirstName= “Mohan”;
string Fname(First name);
string Mname(“Kumar”);
string Sname(“Singh”);
string Halfname, Fullname;
//Joining FirstName with Surname

Halfname.join (Fname, Sname);
//Joining Firstname with Middlename & Surname
Fullname.join (Halfname, Mname);
Fname.display ();
Mname.display ();
Sname.display ();
Halfname.display();

Fullname.displayO();
}
You should see the following output.
/*
Name :- Ram
Name :- Kumar
Name :- Singh
Name:- Mohan .Singh Name :- Mohan.Singh .Kumar
*/
The above program uses new operator to allocate memory. The first constructor is an empty
constructor that allows us to declare an array of string. The second constructor initializes length
of the string, allocates necessary space for the string to be stored and creates the string itself. The
member function join ( ) concatenates 2 strings.
It actually adds the length of 2 strings and then allocates the memory for the combined string.
After that the join function uses inbuilt string functions strcpy & strcat to fulfil the action.
The output of the program will be in Full Name and Half name.
That is Mohan Singh Kumar and Ram Singh respectively.

Another example of the dynamic constructor is the matrix program. In two Dimensional matrix
we need to allocate the memory for the values to be stored in. Using constructor we can allocate
the memory for the matrix.

Task ’Basically, it’s a way of constructing an object based on the run-time type of some
existing object.’ Explain.

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