I'm trying to use `URLComponents` to compose a `URL` as that appears to be what it's for.

However, when I then access the `url` property of the components it is nil.

Example...

```
var urlComponents = URLComponents(string: "http://google.com")!
urlComponents.path = "auth/login"

```

Then I do ...

```
print(urlComponents)

```

Output...

```
scheme: http host: google.com path: auth/login
  - scheme : "http"
  - host : "google.com"
  - path : "auth/login"

```

But then...

```
print(urlComponents.url)

```

outputs `nil`.

Am I doing something wrong with this? How do I get the fully formed URL from all this? Thanks