Destructor:
The purpose of destructor is to free the memory when the compiler memory is reduced or not enough to execute certain program. Sometimes there may several objects opened and it may occupy more memory which may lead to reduced memory for new objects to be created. Therefore to increase the memory; objects which are idle may be destruct or killed using the destructor. The destructor is written in same way as constructor with following rule.
- Destructor should be preceded with (tilde).
- Destructor cannot have any argument or return type.
- Destructor is initiated implicitly.
- One destructor only for each class.
- Destructor must be public.
- Destructor can be defined anywhere in the public generally it is written at the end.
- Destructor can have prototype.
Destructor should have the class name.
class item
{ int number; float cost; public:
void putdata(void)
{cout<<"This is a test for destructor";
}
~item();
};
item::~item()
{cout<<"\nRelease memory\n";}
void main()
{item x;
x.putdata();
}
Note: The ~item is a destructor it will be invoked automatically as soon it the object comes out of the block. There fore destructor should not be called in the main program.
A Sample program of how constructors are defined in different ways.
class item
{ int number;
float cost;
public:
item(void)
{number =10;
cost= 12.34;}
/*item(int x=200)
{number =x;
cost =222.345;} */ item(int a, float b); item(item &x);
void getdata(int a, float b);
//Create inline function inside a class void putdata(void)
{ cout<<"Number:" << number << "\n";
cout<<"Cost:" << cost << "\n";
}
};
void item::getdata(int a, float b)
{ number = a;
cost = b;
}
item::item(int a, float b)
{number =a; cost=b;}
item::item(item &i1)
{number=i1.number; cost=i1.cost;}
void main()
{
clrscr();
{item x; //create object x;
cout<<"\nConstructor without argument"<< "\n";
x.putdata();
}
{int a; float b;
cin>>a>>b;
item x(a,b); //create object x;
cout<<"\nConstructor with dynamic initialization"<< "\n";
x.putdata();
}
{item x(111,123.456); //create object x; cout<<"\nConstructor with arguments"<< "\n"; x.putdata();
item y(x); item z=x; item a; a=x;
cout<<"\nConstructor with object as argument"<< "\n";
y.putdata();
z.putdata();
a.putdata();
}
item y; //create object y; cout<<"\nobject y"<< "\n"; y.getdata(100, 399.95); y.putdata();
}