Copy Constructor & Destructor

1. CHAPTER 8 Copy Constructor & Destructor

2. Session Objectives • Explain Copy Constructor • Conversion Constructor • Explain Destructor • Rules for Framing a Destructor

3. COPY CONSTRUCTOR • This constructor function designed to copy objects of the same class type. • It accepts a single argument and returns a copy of an object • It can also be called if you initialize a new object with another object of same type • Arguments cannot be passed by value • provide way to create a object by making a copy of an existing object

4. Example #include <iostream.h> #include <string.h> #include <conio.h> class item { private : int itno; char itname[20]; float price; public : item(int a,char *b,float c) { itno=a; strcpy(itname,b); price=c; } item(item &ptr) { itno=ptr.itno; strcpy(itname,ptr.itname); price=ptr.price; } void showitem() { cout<<itno<<itname<<price; }};

5. void main() { clrscr(); item i1(1,"Monitor",3800),i2(i1); cout<<"First item"<<endl; i1.showitem(); cout<<"Second item"<<endl; i2.showitem(); getch(); } RESULT First item 1 Monitor 3800 Second item 1 Monitor 3800

6. Destructor Destructor is a special member function that is called automatically when an object is destroyed that have been created by constructor It can be used to deallocate the memory space Need for destructor The programmer is relived of the task of clearing the memory space occupied by the data members every time an object goes out of scope.

7. RULES • It should be declared inside public • It has no return types • It has no argument or parameters • Prefixed by tilde(~) symbol • So a program can have only one destructor Syntax ~Classname( ) { Statements; }

8. Destructor Has to be destroyed complier object calls Destructor De-allocates memory

9. Example for destructor #include<iostream.h> #include<conio.h> class exam { private: int sno,mark1,mark2; public: exam( ) //constructor { sno=mark1=mark2=100; } void showdata() { cout<<sno<<mark1<<mark2 } ~exam() //Destructor { cout<<"destructo is invoked"; }}; void main(){ exam e; e.showdata(); exam e1(1,90,90); clrscr(); e1.showdata(); getch(); } } RESULT Sno = 100 Mark1 = 100 Mark2 =100 Sno = 100 Mark1 = 100 Mark2 =100 destructor is invoked

10. Recursive Function #include<iostream.h> #include<conio.h> void main() { int fact,n; int factorial(int); clrscr(); cout<<"Enter Your Number "<<endl; cin>>n; fact=factorial(n); cout<<endl<<"The Factorial Value is " <<fact; getch(); } int factorial(int x) { if(x==1) return 1; else return x*factorial(x-1); }

11. Summary A constructor is a special member function which is executed automatically when an object is created A Destructor is a special member function which is executed automatically when an object is destroyed

12. EXERCISES • Explain the use of constructors in a class? • Explain the use of Destructors in a class? • State the difference between Constructors & Destructors? • Explain Default constructor with Example? • Explain the use of Copy constructor in a class?