Episode 12: Tagged - help with exercise 8

[tomassliz]

Hello,
I'm going through exercises in episode 12: Tagged and I don't know how to accomplish the last one:

8. Create Unvalidated and Validated tagged types so that you can create a function that takes an Unvalidated and returns an Optional<Validated> given a valid user. A valid user may be one with a non-empty name and an email that contains an @.

I ended up with this:

struct User {
    typealias Id = Tagged<User, Int>
    typealias Name = Tagged<(User, nameTag: ()), String>
    typealias Email = Tagged<(User, emailTag: ()), String>

    let id: Id
    let name: Name
    let email: Email
}

enum UnvalidatedTag {}
typealias Unvalidated<A> = Tagged<UnvalidatedTag, A>

enum ValidatedTag {}
typealias Validated<A> = Tagged<ValidatedTag, A>

func validate(_ user: Unvalidated<User>) -> Validated<User>? {
    let user = user.rawValue

    let isNameValid = !user.name.rawValue.isEmpty
    let isEmailValid = user.email.rawValue.contains("@")

    return (isNameValid && isEmailValid) ? Validated(rawValue: user) : nil
}

let user = Unvalidated(rawValue: User(id: 0, name: "John", email: "[email protected]"))

print(validate(user)?.rawValue ?? "Invalid user")

I don't like the ergonomics of this code - the rawValue is everywhere. When I want to access validated user data I have to call the rawValue for each field.

Can anyone help me with this?