Tuples as Return Types

Probably the next-best tuple use case is using them to return one-time structures. Tuples as return types makes sense when you need to return multiple return types.

The following function is required to return a User from our database. However, in order to speed up processing, the user may be loaded from the cache instead of a query. If that's the case, the caller of the function should also receive the information that the User was cached, and how long it was since the last update from the database. We can easily do this with tuples:

func userFromDatabase(id: Int) -> (user: User, cached: Bool, updated: Date) {

    ...

}

This function returns three values, the actual user user, whether the user is cached cached and when the user was lasted updated.

This also saves you from introducing a new struct type.

Since tuples can also be deconstructed on the fly, this even allows re-introducing the variables at the call site:

let (user, cached, lastUpdated) = userFromDatabase()

This will create three new variables in the current scope: user, cached, and lastUpdated. We will describe this destructuring in more detail in the next chapter.