olbrichj

func fetch(url: URL) -> Promise<Data> {
    return Promise { seal in
        URLSession.shared.dataTask(with: url!) { data, _, error in
            seal.resolve(data, error)
        }.resume()
    }
}

olbrichj

fetch(url: <backend-url>).then { value in
    // value
}

olbrichj

fetch(url: <imageurl>).recover { error -> Promise<UIImage> in
    return UIImage(name: <placeholder>)
}...
  

olbrichj

firstly {
    return fetch(url:url)
}.then{ 
    ...
}

olbrichj

firstly {
    fetch(url: url)
}.ensure {
    cleanup()
}.catch {
    handle(error: $0)
}

olbrichj

func fetch(url: URL) -> Promise<Data> {
    return Promise { seal in
        URLSession.shared.dataTask(with: url!) { data, _, error in
            seal.resolve(data, error)
        }.resume()
    }
}

firstly {

olbrichj

firstly {
    fetch(url: url)
}.get { data in
    //…
}.done { data in
    // same data!
}

olbrichj

firstly {
    when(fulfilled: promise1(), promise2())
}.done { result1, result2 in
    //…
}

olbrichj

fetch(url: url).then(on: .global(QoS: .userInitiated)) {
    //then closure executes on different thread 
}

olbrichj

let waitAtLeast = after(seconds: 0.3)

firstly {
    fetch(url: url)
}.then {
    waitAtLeast
}.done {
    //…
}