constructor related questions

[kumar_mk]

was asked in an interview ---> 1. If the default constructor fails what happens? 2. What is Conversion constructor? Please give a small code example. 3. Why there is no virtual constructor? thanx in advance kumar_windows

[Ryan Binns]

1. Fails? In what way? If an exception is thrown, it's the same as if any other exception is thrown. The object is left in an undefined state, and should not be used. 2. A constructor that can be used to convert between different types. It takes one argument, and allows you to typecast from the argument type to the class type. 3. Because when you create a class, the compiler has to know exactly what type it is. The virtual function pointer table is initialised as part of the constructor call, so there is no way to implement a virtual function lookup until after the constructor completes.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

[Laxman Auti]

kumar_windows wrote:

If the default constructor fails what happens?

http://burks.bton.ac.uk/burks/language/cpp/cppfaq/exceptio.htm#[17.1][^]

kumar_windows wrote:

2. What is Conversion constructor? Please give a small code example.

A constructor that accepts one argument of a different type For e.g

CDemo d{
int m_i;
public:
CDemo(int i){
m_i=i;
}
};

kumar_windows wrote:

Why there is no virtual constructor?

There is nothing like Virtual Constructor. The Constructor can’t be virtual as the constructor is a code which is responsible for creating a instance of a class and it can’t be delegated to any other object by virtual keyword means. Knock out 't' from can't, You can if you think you can :cool: