重试延迟 - RxSwift

Posted 2023-03-14

【中文标题】重试延迟 - RxSwift

【英文标题】：Delay for Retry - RxSwift

【发布时间】：2016-11-25 05:51:39

【问题描述】：

有没有优雅的解决方案来为retry 创建延迟？发生错误时，我想等待 5 秒并重新启动 Observable (retry)

【参考方案1】：

这里是swift 4.0+的代码

// sample retry function with delay
private func sampleRetryWithDelay()
    let maxRetry = 3
    let retryDelay = 1.0 // seconds
    let _ = sampleStreamWithErrors() // sample observable stream, replace with the required observable
        .retryWhen  errors in
            return errors.enumerated().flatMap (index, error) -> Observable<Int64> in
                return index < maxRetry ? Observable<Int64>.timer(RxTimeInterval(retryDelay), scheduler: MainScheduler.instance) : Observable.error(error)
            
        .subscribe(onNext: value in
            print("Result:\(value)")
        )


// Sample stream with errors, helper function only - generating errors 70% of the time
private func sampleStreamWithErrors() -> Observable<Int>
    return Observable.create  observer in
        let disposable = Disposables.create()  // nothing to cancel, we let it complete
        let randomInt = Int(arc4random_uniform(100) + 1)
        if randomInt > 70 
            observer.on(.next(randomInt))
            observer.on(.completed)
         else 
            let sampleError = NSError(domain: "SampleDomain", code: randomInt, userInfo: nil)
            print("Result:Error:\(randomInt)")
            observer.on(.error(sampleError))
        
       
        return disposable
    

【参考方案2】：

只需创建一个环绕 retry() 的 PrimitiveSequence 扩展。 (Swift5.1 RxSwift 4.3.1)

extension PrimitiveSequence
  func retry(maxAttempts: Int, delay: TimeInterval) -> PrimitiveSequence<Trait, Element> 
    return self.retryWhen  errors in
      return errors.enumerated().flatMap (index, error) -> Observable<Int64> in
        if index < maxAttempts 
          return Observable<Int64>.timer(RxTimeInterval(delay), scheduler: MainScheduler.instance)
         else 
          return Observable.error(error)
        
      
    
  

使用示例：（重试3次，每次延迟2秒）

yourRxStream.retry(maxAttempts: 3, delay: 2)