Updating periodically with RxSwift

Question

I use the following setup to retrieve objects (e.g. GitHub issues) from an API. This works fine.

let provider: RxMoyaProvider<GitHub>
let issues: Driver<[IssueViewModel]>

init(provider: RxMoyaProvider<GitHub>) {
    self.provider = provider
    issues = provider.request(.Issue)
              .mapArray(Issue.self, keyPath: "issues")
              .asDriver(onErrorJustReturn: [])
              .map { (models: [Issue]) -> [IssueViewModel] in
                  let items = models.map {
                      IssueViewModel(name: $0.name,
                          description: $0.description
                      )
                  }
                  return items
              }
}

Now I'd like to periodically update the list of issues (e.g., every 20 seconds). I thought about an NSTimer to accomplish this task, but I guess there might be a clean(er) solution (i.e. in a Rx manner) that I didn't think about.

Any hint in the right direction is highly appreciated.

score 13 · Accepted Answer · edited May 23 '17 at 12:24

13

This is very similar to this question/answer.

You should use timer and then flatMapLatest:

Observable<Int>.timer(0, period: 20, scheduler: MainScheduler.instance)
    .flatMapLatest { _ in
        provider.request(.Issue)
    }
    .mapArray(Issue.self, keyPath: "issues")
    // ...

edited May 23 '17 at 12:24

Community

1
1

answered Sep 07 '16 at 07:59

solidcell

7,639
4
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59

This is great, thanks! Given that .Issue expects a parameter (e.g., `.Issue(id: issueId)`), how to reference this in `flatMapLatest` (`issueId` is a stored property)? – tilo Sep 07 '16 at 08:23
use `.flatMapLatest { [weak self] _ in` in the block and then `self?.issueId`. – solidcell Sep 07 '16 at 08:25
Hello from the future! You might wish to use `concatMap` if you want to process the requests in order. – Przemysław Wrzesiński Jan 31 '20 at 08:16

Eluss · Answer 2 · 2016-09-06T21:25:35.687

3

You are probably looking for interval operator. Here is a loop example for interval that will keep printing "test" every second. Link to documentation: http://reactivex.io/documentation/operators/interval.html

    var driver: Driver<String> {
        return Driver<Int>.interval(1.0).map { _ in
            return "test"
        }
    }
    driver.asObservable().subscribeNext { (variable) in
        print(variable)
    }

edited Sep 06 '16 at 21:25

answered Sep 06 '16 at 20:38

Eluss

512
3
5

Thanks for your answer. But how do you apply this to a `Driver`? – tilo Sep 06 '16 at 20:46
It looks like interval works with `Drivers` as well. I've updated previous example – Eluss Sep 06 '16 at 21:26
Great, but how can I apply this to my specific example? – tilo Sep 07 '16 at 06:31

Updating periodically with RxSwift

2 Answers2