CONSTRUCTORS AND DESTRUCTORS

CONSTRUCTORS AND DESTRUCTORS
Q: Is it possible to have Virtual Constructor? If yes, how? If not, Why not possible?
A: There is nothing like Virtual Constructor. The Constructor can’t be virtual as the constructor
is a code which is responsible for creating an instance of a class and it can’t be delegated to
any other object by virtual keyword means.
Q: What is constructor or ctor?
A: Constructor creates an object and initializes it. It also creates vtable for virtual functions. It is
different from other methods in a class.
Q: What about Virtual Destructor?
A: Yes there is a Virtual Destructor. A destructor can be virtual as it is possible as at runtime
depending on the type of object caller is calling to, proper destructor will be called.
Q: What is the difference between a copy constructor and an overloaded assignment operator?
A: A copy constructor constructs a new object by using the content of the argument object. An
overloaded assignment operator assigns the contents of an existing object to another existing
object of the same class.
Q: Can a constructor throws an exception? How to handle the error when the constructor fails?
A:The constructor never throws an error.
Q: What is default constructor?
A: Constructor with no arguments or all the arguments has default values.
Q: What is copy constructor?
A: Constructor which initializes the it's object member variables ( by
shallow copying) with another object of the same class. If you don't implement one in your class
then compiler implements one for you. for example:
(a) Boo Obj1(10); // calling Boo constructor
(b) Boo Obj2(Obj1); // calling boo copy constructor
(c) Boo Obj2 = Obj1;// calling boo copy constructor
Q: When are copy constructors called?
A: Copy constructors are called in following cases:
(a) when a function returns an object of that
class by value
(b) when the object of that class is passed by
value as an argument to a function
(c) when you construct an object based on another
object of the same class
(d) When compiler generates a temporary object
Q: Can a copy constructor accept an object of the same class as parameter, instead of reference
of the object?
A: No. It is specified in the definition of the copy constructor itself. It should generate an error if
a programmer specifies a copy constructor with a first argument that is an object and not a
reference.
Q: What is conversion constructor?
A: constructor with a single argument makes that constructor as conversion ctor and it can be
used for type conversion.
for example:
class Boo
{
public:
Boo( int i );
};
Boo BooObject = 10 ; // assigning int 10 Boo object
Q:What is conversion operator??
A:class can have a public method for specific data type conversions.
for example:
class Boo
{
double value;
public:
Boo(int i )
operator double()
{
return value;
}
};
Boo BooObject;
double i = BooObject; // assigning object to variable i of type double.
now conversion operator gets called to assign the value.
Q: How can I handle a constructor that fails?
A: throw an exception. Constructors don't have a return type, so it's not possible to use return
codes. The best way to signal constructor failure is therefore to throw an exception.