ios - `flatMap` 发布者有不同的错误

Question

我有一个像下面这样的 Swift 发布者

let item = PassthrogutSubject<String, Never>()

收到字符串后，我想发出网络请求
为此，我正在使用 flatMap我的网络请求签名如下所示:

func loadDetails(_ code: String) -> AnyPublisher<CustomType, ErrorAlert>

我怎样才能做到以下几点:

$item
 .filter { !$0.isEmpty }
 .flatMap { [unowned self] (string) in
    self.viewModel.loadDetails(string) }
 .receive(on: DispatchQueue.main)
 .sink(receiveCompletion: { _ in
     ...
  }) {  ... }
 .store(in: &subscriptions)

错误: Instance method 'flatMap(maxPublishers:_:)' requires the types 'Published<Value>.Publisher.Failure' (aka 'Never') and 'Alert' be equivalent

Answer 1

在我的问题进行到一半时，我在接收第一个订户时与以下运算符(operator)一起解决了这个问题

$item
 .filter { !$0.isEmpty }
 .setFailureType(to: ErrorAlert.self) // <---- 💯 HERE
 .flatMap { [unowned self] (string) in
    self.viewModel.loadDetails(string) }
 .receive(on: DispatchQueue.main)
 .sink(receiveCompletion: { _ in
     ...
  }) {  ... }
 .store(in: &subscriptions)