Constructor overloading in C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is constructor overloading in C++?

Constructor overloading means having multiple constructors in a class with different parameters. This lets you create objects in different ways depending on the data you provide.

beginner

Why do we use constructor overloading?

We use constructor overloading to give flexibility when creating objects. It allows initializing objects with different sets of data without writing separate functions.

intermediate

How does the compiler decide which constructor to call?

The compiler looks at the number and types of arguments you pass when creating an object. It matches these to the constructor with the same parameter list.

intermediate

Can constructors have default parameters in constructor overloading?

Yes, constructors can have default parameters. But be careful because default parameters can cause ambiguity if multiple constructors match the call.

beginner

Example of constructor overloading in C++?

class Box {
public:
  Box() { /* no-arg constructor */ }
  Box(int l, int w, int h) { /* 3-arg constructor */ }
  Box(int size) { /* 1-arg constructor */ }
};

This class has three constructors with different parameters.

What does constructor overloading allow you to do?

A Create multiple constructors with different parameters

B Create only one constructor per class

C Change the return type of constructors

D Use constructors without parameters only

Constructor overloading means having multiple constructors with different parameter lists.

If a class has constructors Box() and Box(int size), which constructor is called by Box b(5)?

A Both

B Box()

C Box(int size)

D None

Box b(5) matches the constructor with one int parameter.

What happens if two constructors have the same parameter types and counts?

A The first constructor is always called

B Compiler error due to ambiguity

C The last constructor is always called

D It works fine without errors

Constructors must differ in parameter types or counts to avoid ambiguity.

Can constructors have default arguments in constructor overloading?

A Yes, but it can cause ambiguity

B No, default arguments are not allowed

C Yes, and it never causes problems

D Only for destructors

Default arguments are allowed but can cause ambiguity if multiple constructors match.

Which of these is NOT a valid constructor overloading example?

A Box() {} and Box(int a) {}

B Box(int a, int b) {} and Box(int a) {}

C Box(double a) {} and Box(int a) {}

D Box(int a) {} and Box(int b) {}

Two constructors with the same parameter types and counts cause errors.

Explain constructor overloading and why it is useful in C++.

Think about how you can create objects in different ways.

Describe how the compiler chooses which constructor to call when you create an object.

Focus on how the arguments you provide relate to constructors.