Gain insights into the C++ keyword 'const,' its usage in various contexts, and implications when returning pointers and references. Learn about preventing accidental data changes.

How to use const in C++ by Sándor Dargo_468 x 60 copy.png

In this course, you will learn about the C++ keyword const and its behaviour under different usage conditions, including local, global and static contexts. This course will help you to understand const and its implications when you attempt to return pointers and references in C++. By the end of the course, you will have a solid grip on const and its usage in preventing any accidental change of data.

Secure Coding Practices in C++: A Deep Dive into const

A function can return values, references, and pointers, and all of these can be `const`. However, does it make sense to convert them to `const`? Let’s find out!

# Returning `const` objects by value

The first-time `const` users might get enthusiastic about turning everything into `const` and might start converting signatures like `std::string getName()` into `const std::string getName() const`. However, it's not a great idea to turn all the return values into `const`.

Why is that so?

The `const` qualifier shows the reader and compiler that something should not be modified. When we return something by value, it makes a copy for the caller. 

Does it make sense to make a copy `const`?

Imagine buying a house, and not being allowed to modify it. In most cases,  you want your house to be your castle. It is similar to the relationship between our copy and our object. We want to be able to do whatever we want to the copy.

A `const` object doesn’t make sense when it is returned by the value. It's misleading and might even be harmful.

How can it be harmful?

## Move for non-`const` return types
The move is possible for non-`const` return types. Let’s say we have the following  code:

Let’s learn about the kinds of variables a function can return.

Introduction

Arguments using const

Local Variables

Local Members

Functions

Return Types

const Parameters

const and Smart Pointers

Rvalue References

Summary

const Return Types

Returning `const` objects by value

const Return Types

Returning const objects by value

Returning `const` objects by value