C++ Constructors & Function Overloading Interview Questions

C++ Constructors

Basic Level (15 Questions)

What is a constructor in C++?

A constructor is a special member function that initializes objects of a class. It has the same name as the class, no return type (not even void), and is automatically called when an object is created.

What are the different types of constructors in C++?

C++ has several constructor types: Default constructor (no parameters), Parameterized constructor (with parameters), Copy constructor (creates object as copy), Move constructor (C++11, transfers resources), and Delegating constructor (C++11, calls another constructor).

What is a default constructor?

A default constructor is a constructor that can be called with no arguments. It either has no parameters or all parameters have default values. If no constructor is defined, compiler provides an implicit default constructor.

What is a copy constructor?

A copy constructor creates a new object as a copy of an existing object. It takes a reference to an object of the same class as its parameter: ClassName(const ClassName &obj). Used when objects are passed by value, returned by value, or explicitly copied.

When is a copy constructor called?

A copy constructor is called in these situations: 1) When an object is passed by value to a function, 2) When an object is returned by value from a function, 3) When an object is initialized using another object of the same class, 4) When compiler creates a temporary object.

What is a destructor in C++?

A destructor is a special member function that cleans up resources when an object is destroyed. It has the same name as the class preceded by a tilde (~), takes no parameters, and has no return type. Called automatically when object goes out of scope.

What is constructor overloading?

Constructor overloading is defining multiple constructors with different parameter lists in the same class. This allows objects to be initialized in different ways. Example: Rectangle(), Rectangle(int w), Rectangle(int w, int h).

What is the difference between initialization list and assignment in constructors?

Initialization list directly initializes member variables: ClassName() : member1(value1), member2(value2) {}. Assignment sets values in constructor body. Initialization list is more efficient, especially for const members and references which must be initialized.

What is a delegating constructor (C++11)?

A delegating constructor is a constructor that calls another constructor of the same class in its initialization list. This avoids code duplication. Syntax: ClassName() : ClassName(defaultValue) {}

What is the Rule of Three/Five in C++?

The Rule of Three: If a class needs a custom destructor, copy constructor, or copy assignment operator, it likely needs all three. The Rule of Five (C++11): Adds move constructor and move assignment operator to the rule.

Review question