4

I am using RxMoya for the network layer of my app and I'm having a case where the server can either send the expected response (let's say a User), or an error object, both with status code 200. For example:

{
  "name": "john doe",
  "username": "john_doe"
}

could be the expected response and 

{
  "error": {
    "code": 100,
    "message": "something went wrong™"
  }
}

could be the error.

The relevant part of the network adapter could look like this:

    return provider
        .rx
        .request(MultiTarget.target(target))
        .map(User.self)
        // if above fails, try:
        // .map(UserError.self)
        .asObservable()

Is there a way to firstly try and .map(User.self) and if that fails, try to .map(UserError.self) in the same chain of operations? In other words, could I provide an alternative mapping model using Rx?

phi
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1 Answers1

4

You could use flatMap to do that. Something like this: 

    return provider
    .rx
    .request(MultiTarget.target(target))
    .flatMap { response -> Single<User> in
        if let responseType = try? response.map(User.self) {
            return Single.just(responseType)
        } else if let errorType = try? response.map(UserError.self) {
            return Single.error(errorType.error)
        } else {
            fatalError("⛔️ We don't know how to parse that!")
        }
     }

BTW, status code 200 to return an error is not correct.

phi
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davebcn87
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  • Sorry, somehow I missed your answer. The problem is that I want to return a `Single.just(user)` in the first case and a `Single.error(errorMessage)` in the second. In your code, what does the line `if let user = User.self` do? – phi Sep 06 '18 at 15:23
  • Ok, got it. Since you deserve the points, I'm editing your answer a bit before accepting it. Thanks! – phi Sep 06 '18 at 15:38
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    Ok, I thought `User.self` was optional and did the unwrap with the `if let`. But yes, you can return `Single.just(user)` and `Single.error` but the error should have an `Error` object and not a string. Also, if the return type of the `flatMap` is `Single` you can type directly `.just(user)` and `.error(error)` – davebcn87 Sep 06 '18 at 15:42