RxSwift + MVVM +协调器模式，如何依次等待协调器结果？

Question

场景：

我有基本的协调员，基本上像这样：

class Coordinator<Result> {
   // some coordinator class codes

   func coordinate(to: Coordinator<T>) -> Observable<T> {
       return coordinator.start()
   }

   func start() -> Observable<Result> {
      // return result
   }
} 

和TestCoodinator1，TestCoordinator2，TestCoodinator3一样，如下所示：

enum Status {
    case .success(data: NSData?)
    case .cancelled(error: NSError?)
    case .failed(data: NSData?)
}

class TestCoordinator1: Coordinator<Status> {
     // Init pass UINavigationController as rootViewController

     let testVC1 = TestViewController1()
     let testVM1 = TestViewModel1()
     testVC1.viewModel = testVM1         

     return testVM1.status // returns Observable<Status>
         .do(onNext: { [unowned self] _ in self?.rootViewController.popViewController(animated: true)
} 

我有一个主要的协调员，基本上像这样：

class MainCoordinator: Coordinator<Void> {

    override func start() -> Observable<Void> {
        let mainVC = MainVC()
        let mainVM = MainVM()
        mainVC.viewModel = mainVM

        let testCoordinator1 = TestCoordinator1(in: rootViewController)
        let viewModel1 = ViewModel1()
        testCoordinator1.viewModel = viewModel1

        let testCoordinator2 = TestCoordinator2(in: rootViewController)
        let viewModel2 = ViewModel2()
        testCoordinator2.viewModel = viewModel2

        let testCoordinator3 = TestCoordinator3(in: rootViewController)
        let viewModel3 = ViewModel3()
        testCoordinator3.viewModel = viewModel3

        // viewModel.tests returns Observable that has three types of tests randomly generated
        // Observable.of("Test1", "Test2", "Test3")
        mainVM.tests ????

        return Observable.never()
    }
}

问题：

如何创建可协调到test1的可观察对象，并首先等待test1完成，然后对结果进行一些处理，然后才运行test2，处理一些结果，然后运行test3。

如果我这样做：

mainVM.tests
   .flatMap { test in 
       switch(test) {
           case "Test1":
                 return self.coordinate(to: testCoordinator1)
           case "Test2":
                 return self.coordinate(to: testCoordinator2)
           case "Test3":
                 return self.coordinate(to: testCoordinator3)
       }
   }
   .subscribe(onNext: { status in 
      self.processStatus(status)
   })

所有三个协调员同时运行

Answer 1

如果我对您的理解正确，则可以通过链接可观察对象来实现：

mainVM.tests
    .flatMapLatest { test -> Observable<...> in
        // do some things
        return self.coordinate(to: testCoordinator1)
    }
    .flatMapLatest { _ -> Observable<...> in
        // handle first coordinator
        return self.coordinate(to: testCoordinator2)
    }
    .flatMapLatest { _ -> Observable<...> in
        // handle second coordinator
        return self.coordinate(to: testCoordinator3)
    }
    .flatMapLatest { _ -> Observable<...> in
        // handle third coordinator
    }
    .subscribe(onNext: { status in
        self.processStatus(status)
    })