在块中不需要返回：

.then { obj -> Location in
      Swift.getLocation("433434").then{ location in
          self.locationUUID = location.get("uuid")
      }
}

这里有很多问题。
1.你没有锁链，因为你没有回报你的承诺。
1.在第二个闭包中没有返回，这是编译错误，闭包说它返回Location，但闭包返回Void
。

Swift.start(host, "", "").then { result -> Void in

}.then { obj -> Promise<Something> in
    print(obj)

    // I changed the return of this closure, see above
    // we must return the promise or we are not chaining
    return Swift.getCurrent.then { obj -> Void in
        let payload: Dictionary<String, AnyObject> = obj as! Dictionary<String, AnyObject>
        self.deviceUUID = payload["uuid"] as! String

    }
}.then { obj -> Location in
    println(obj)

    // we promised a return value above, so we must return
    return Swift.getLocation("3333").then { location in
        self.locationUUID = location.get("uuid")
    }
}

然而，看看你的代码，它似乎是不正确的，这是你真正想要的吗？

firstly { _ -> Promise<[String: AnyObject]> in
    return Swift.getCurrent
}.then { payload -> Promise<Location> in
    self.deviceUUID = payload["uuid"] as! String
    return Swift.getLocation("3333")
}.then { location -> Void in
    self.locationUUID = location.get("uuid")
}