TriplePromiseWhen.swift

firstly {
    // Execute all promises simultaneously
    when(fulfilled: firstPromise(), secondPromise(), thirdPromise())
}.done { first, second, third in
    // Once they all complete, data will be available here
    let newData = [first, second, third].flatMap { return $0 }
    process(newData)
}.catch { error in
    print("Error: ", error.localizedDescription)
}