let credentials = Publishers
    .CombineLatest($username, $password) { ($0, $1) }
    .share()
credentials
    .map { uname, pass in
        uname.count >= 4 && pass.count >= 4
    }
    .prepend(false) // initial state
    .assign(to: \.isEnabled, on: loginButton)
    .cancelled(by: cancellableBag)
    // More in the example...

Timer.publish(every: 0.1, on: .main, in: .default)
    .autoconnect()
    .scan(0, { (acc, _ ) in return acc + 1 })
    .map { $0.timeInterval }
    .replaceError(with: "")
    .eraseToAnyPublisher()
    .assign(to: \.currentTime, on: self)
    .cancelled(by: cancellableBag)
    // More in the example...

$query
    .throttle(for: 0.5, 
        scheduler: .main, 
           latest: true)
    .removeDuplicates()
    .map { query in
        return API().search(with: query)
            .retry(3)
            .eraseToAnyPublisher()
    }
    // More in the example...

 $text
    .throttle(for: 0.5, scheduler: .main, latest: true)
    .map { text in
        API().search(with: text)
            .map { isAvailable in
                isAvailable ? "Name available" : "Name already taken"
            }
            .prepend("Checking...")
    }
    .switchToLatest()
    // More in the example...