Understanding Auth.auth() in Firebase

In getting started with Firebase Authentication in iOS, the way you can handle most of the authentication processes uses Auth.auth() as indicated in the snapshot below:

It seems redundant (at least initially). If you read it, it seems like it is calling Auth twice to do its job, but I think most people would understand it once they searched for the answers, which I did and will share in this writing.

What the Documentation Has to Say

Well, if you look at the documentation, it has no resources that explain why Auth.auth() is the convention. So I suspect that this convention is “internally understood,” but I don’t understand it yet, which is why I want to learn more about it.

The first step is understanding what does Auth mean.

It says here that Auth is a class and auth() is a method of that class that gets the auth object, as shown in the definition.

And that’s actually it; seems easy enough!

What Xcode Has to Say

Let’s evaluate this working code by trying to remove the Auth class

And that’s the key!

By using auth() only, Xcode has no idea where to find it. Because remember that in most libraries that you would use in Swift language, every method lives inside a construct, either in protocols, structs, or classes.

What I suspect in this one is that it tries to search globally by default if the auth() function exists. It seems that by importing FirebaseAuth, it does not register its methods in the global function scope to be used implicitly.

The use of the Auth class prefix makes it so that when you write Auth.auth(), Swift can recognize the Auth class from the imported FirebaseAuth library, and execute the auth() method that resides within that class.

There you have it! It’s very easy to understand once you think of it that way, but it will not always be obvious if you are just starting out.