How to write a singleton in Swift

I’m as opposed to singletons as anyone else in general due to the fact that they make testing harder, but sometimes, like when managing access to a local SQLite database, I want to make sure there’s only one instance of the class that purges old records from it. So a singleton seems to make sense. But how do we do that in Swift?

class SQLiteManager {
    static let shared = SQLiteManager()

    private init() {}
}

The static let here will only instantiate our SQLiteManager once, and the private initializer ensures that no one else calls init on our SQLiteManager.

Now we can call SQLiteManager.shared.purgeObsoleteRecords() and get rid of those old bits we don’t need any more, freeing up some storage for our user.