const Return Types

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: