ThreeFunctions.swift

func requestFirstData() {
    firstly {
        firstPromise()
    }.done { data in
        self.process(content: data)
    }.catch { error in
        print("Error: ", error.localizedDescription)
    }
}

func requestSecondData() {
    firstly {
        secondPromise()
    }.done { data in
        self.process(content: data)
    }.catch { error in
        print("Error: ", error.localizedDescription)
    }
}

func requestThirdData() {
    firstly {
        thirdPromise()
    }.done { data in
        self.process(content: data)
    }.catch { error in
        print("Error: ", error.localizedDescription)
    }
}