C++ : Constructors And Destructors

Constructors

Constructor functions are the special functions which if present automatically get executed whenever an object of a class is declared.

Properties

• Name of the constructor function is exactly same as that of the class.
• It has no return type not even void
• If present it automatically gets executed whenever an object of a class is declared
• It cannot be invoked/called using an object of the class.
• It is generally used to initialize the data elements of an object at the time of declaration.

There are three types of constructors

• Default constructors
• Parameterized constructors
• Copy constructors

Default constructors

Default Constructor is a special function which if present automatically gets executed whenever an object of a class is declared without any parameters.

Example:
student s;
employee e;

Properties

• Name of the default constructor function is exactly same as that of the class.
• It has no return type not even void
• If present it automatically gets executed whenever an object of a class is declared without any parameters.
• It cannot be invoked using an object of the class.
• It is generally used to initialize the data elements of an object at the time of declaration by user-defined values.
• We do not pass any arguments in the default constructor.
• Default constructor cannot be overloaded.
• Default constructors gets called only once for an object when it is declared without parameters.

Question:
How many default constructors can be present in a class? Why?
Sol:

There can be only one default constructor in the class.(the reason we do not pass any arguments to a default constructor and hence cannot be overloaded).

Question:
Why default constructors cannot be overloaded? Give reason.
Sol:

As we do not pass any arguments to a default constructor and so cannot be overloaded.

 

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