call func in Asynchronous requests chaining RxSwift and Alamofire

Question

I'm a begginer with RxSwift and this is my issue, my app must do a 3 requests, the 3 are gets, my work team suggests me use a flatmap to do this a three request in row, but I don't know how I should use flatmap.

these are my requests

public func login(param: [String:String]) -> Observable<messageModel>{
        return Observable.create { observer -> Disposable in
            self.alamoFireManager!.request(self.urlServer!+endPoints.login.login, method: .post, parameters: param, encoding: URLEncoding.default, headers: nil, interceptor: nil).responseDecodable { (res: DataResponse<messageModel,AFError>) in
                if let error = res.error {
                    observer.onError(error)
                } else if let valueEntitie = res.value {
                    observer.onNext(valueEntitie)
                }
                observer.onCompleted()
            }
            return Disposables.create()
        }
    }


public func me()  -> Observable<meModel>{
        return Observable.create { observer -> Disposable in
            self.alamoFireManager!.request(self.urlServer!+endPoints.login.me, method: .get, parameters: nil, encoding: URLEncoding.default, headers: nil, interceptor: nil).responseDecodable { (res: DataResponse<meModel,AFError>) in
                if let error = res.error {
                    observer.onError(error)
                } else if let valueEntitie = res.value {
                    observer.onNext(valueEntitie)
                }
                observer.onCompleted()
            }
            return Disposables.create()
        }
    }


public func entitie(entityId: String) -> Observable<entitieModel>{
        return Observable.create { observer -> Disposable in
            self.alamoFireManager!.request(self.urlServer!+endPoints.login.entities+"/"+entityId, method: .get, parameters: nil, encoding: URLEncoding.default, headers: nil, interceptor: nil).responseDecodable { (res: DataResponse<entitieModel,AFError>) in
                if let error = res.error {
                    observer.onError(error)
                } else if let valueEntitie = res.value {
                    observer.onNext(valueEntitie)
                }
                observer.onCompleted()
            }
            return Disposables.create()
        }
    }

the first endpoint is login with its parameters, then me, function me response a id, this id its necessary for the third request, that is entitie.

I'm doing the flatmap as this way.

networkManagerShareCore.share.login(param: param)
                .flatMap { resMessageModel in
                    //saveData(resMessageModel)
                    networkManagerShareCore.share.me()
                        .flatMap { resMeModel in
                         //saveData(resMessageModel)
                         networkManagerShareCore.share.entitie(entityId: "\(resModelMe.data.personId!)")
                    }
            }.subscribe(onNext: { (model) in
                print(model)
            }, onError: { (error) in
                self.errorMsg.accept(error.localizedDescription)
                self.isSuccess.accept(false)
            }, onCompleted: nil) {
                print("Disposed")
            }

the code works, but in the line //saveData(resMessageModel) I can't call it the function, I want to save the model, but if I try a call a function, Xcode show me this error: Unable to infer complex closure return type; add explicit type to disambiguate so, how can I resolve this?

Answer 1

Dale's answer works but I would be inclined to move the saves into do operators instead. Like this:

networkManagerShareCore.share.login(param: param)
    .do(onNext: { [weak self] resMessageModel in
        self?.saveData(resMessageModel)
    })
    .flatMap { _ in
        networkManagerShareCore.share.me()
    }
    .do(onNext: { [weak self] resMeModel in
        self?.saveData(resMeModel)
    })
    .flatMap { resMeModel in
        networkManagerShareCore.share.entitie(entityId: "\(resMeModel.data.personId!)")
    }
    .subscribe(
        onNext: { (model) in
            print(model)
        },
        onError: { (error) in
            self.errorMsg.accept(error.localizedDescription)
            self.isSuccess.accept(false)
        },
        onCompleted: nil,
        onDisposed: {
            print("Disposed")
        }
    )
    .disposed(by: disposeBag)

Answer 2

RxSwift flatMap expects a return value of some Observable.

The FlatMap operator transforms an Observable by applying a function that you specify to each item emitted by the source Observable, where that function returns an Observable that itself emits items.

You need to add a return statement within each flatMap call. In addition, you need to explicitly define the return type for the closures.

So the inner most flatMap call should look something like this:

 networkManagerShareCore.share.me()
       .flatMap { resMeModel -> Observable<entitieModel> in
             //saveData(resMessageModel)
             return networkManagerShareCore.share.entitie(entityId: "\(resModelMe.data.personId!)")

You wouldn't normally embed flatMap within flatMap, but just compose them sequentially to make the code clearer. And don't forget disposed(by:). The final result would look something like this:

networkManagerShareCore.share.login(param: param)
    .flatMap { resMessageModel -> Observable<meModel> in
          //saveData(resMessageModel)
          return networkManagerShareCore.share.me()
     }
     .flatMap { resMeModel -> Observable<entitieModel> in
           //saveData(resMessageModel)
           return networkManagerShareCore.share.entitie(entityId: "\(resModelMe.data.personId!)")
     }
     .subscribe(
         onNext: { (model) in
                  print(model)
         }, 
         onError: { (error) in
            self.errorMsg.accept(error.localizedDescription)
            self.isSuccess.accept(false)
         }, 
         onCompleted: nil) {
            print("Disposed")
     }
     .disposed(by: disposeBag)