ios – Combine Subscriber not receiving values immediately

By
Channel969
-
0
193


I am trying to come up with a Combine pipeline that does the following

  • Make an API call with certain pageIndex and send the results to subscriber
  • Increment the page Index and repeat the above until backend says there is nothing more to fetch

Here is what I have done so far

struct APIResponse {
  var hasNextPage: Bool = false
  var nextPageIndex: Int = -1
}
class Tester {
    func getAllDetails() -> AnyPublisher<APIResponse, Never> {
        // Subject holding the page index to be fetched
        let subject = CurrentValueSubject<Int, Never>(0)
        
        return subject.flatMap ({ index in
            return self.getDetails(index: index)
        })
        .handleEvents(receiveOutput: { response in
            if response.hasNextPage {
                subject.send(response.nextPageIndex)
            } else {
                subject.send(completion: .finished)
            }
        })
 // Ignore the call, Just did it please the compiler
        .replaceError(with: APIResponse())
        .eraseToAnyPublisher()
    }
    
    func getDetails(index: Int) -> AnyPublisher<APIResponse,MockError> {
        Future { promise in
            // Mocking API Response here
            if index < 5 {
                promise(.success(APIResponse(hasNextPage: true, nextPageIndex: index+1)))
            } else if index == 5 {
                promise(.success(APIResponse(hasNextPage: false)))
            } else {
                promise(.failure(MockError()))
            }
        }
        .eraseToAnyPublisher()
    }
}

let tester =  Tester()
tester.getAllDetails()
    .sink { _ in
        print("completed")
    } receiveValue: { numbers in
        print(numbers.debugDescription)
    }

The pipeline is working but it delivering all the results to subscriber at the end and not as they arrive. How do I change this to let subscriber receive intermediate values