Type Conversions

In C++ expressions, the user-defined and built-in types are applied together. The compiler has no idea about user-defined data types and conversion to other data types. To overcome this problem, the programmer must design the procedures that convert basic data types to user-defined data types and vice versa.

There are three possibilities.

·         Conversion from Basic to class type

·         Conversion from Class to Basic Type

·         Conversion from one class Type to another Class Type

 

1. Conversion from Basic to Class type

In C++, a variable of basic data type will be converted into a data member of a class.

A Constructor is used for conversion.

Example:

String(char *s)

{

Strcpy(str,s);

}

We invoke the constructor

String s1= “Hello!”;

(or)

String s1(“Hello!”);

Here string object is built from the basic data type of char.

2. Conversion from Class type to Basic Data Type

In C++, A user-defined data type can also be converted into a basic data type.

Overloaded casting operator is used for conversion.

The syntax for an overloaded operator is:

Operator type_name()

{

-------

}

Note:

·         The function does not have any return type

·         The function converts the class type into the type_name

·         The function does not take any arguments.

 

3. Conversion from class to class type

In C++, an object of one class is converted into that of another class.

Syn:- obj_dest = obj_source;

This conversion can be implemented in two ways

·         Using a constructor (Conversion in destination class)

 Using casting operator function  (Conversion in the source class)

 

Conversion in the source class

When performing conversion in the source class, a type cast operator is used.

Syntax:-

operator typename()

{

--------

}

Operator is the keyword, typename refers the destination type.

Conversion in destination class

When performing conversion in the destination class, a single argument constructor is used where argument is the object of the source class.

Syntax:-

class1( class2 obj)

{

--------

}

};