注意：使用本例中的代码首先应该导入头文件，代码如下：

import RxSwift

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Error Handling Operators

该操作帮助重新覆盖来自Observable的错误通知。

catchErrorJustReturn

通过返回一个发散单一元素且随后终止的Observable序列来重新覆盖一个 Error 事件。了解更多

example("catchErrorJustReturn") {
    let disposeBag = DisposeBag()

    let sequenceThatFails = PublishSubject<String>()

    sequenceThatFails
        .catchErrorJustReturn("😊")
        .subscribe { print($0) }
        .disposed(by: disposeBag)

    sequenceThatFails.onNext("😁")
    sequenceThatFails.onNext("😨")
    sequenceThatFails.onNext("😡")
    sequenceThatFails.onNext("🔴")
    sequenceThatFails.onError(TestError.test)
}

Debug Area 输出：
--- catchErrorJustReturn example ---
Next(😬)
Next(😨)
Next(😡)
Next(🔴)
Next(😊)
Completed

---

catchError

通过切换到另一个具有恢复功能的Observable序列的方式来覆盖 Error 事件。�了解更多

example("catchError") {
    let disposeBag = DisposeBag()

    let sequenceThatFails = PublishSubject<String>()
    let recoverSequence = PublishSubject<String>()

    sequenceThatFails
        .catchError {
            print("Error:", $0)
            return recoverSequence
        }
        .subscribe { print($0) }
        .disposed(by: disposeBag)

    sequenceThatFails.onNext("😬")
    sequenceThatFails.onNext("😨")
    sequenceThatFails.onNext("😡")
    sequenceThatFails.onNext("🔴")
    sequenceThatFails.onError(TestError.test)
    
    recoverySequence.onNext("😊")
}

Debug Area 输出：
--- catchError example ---
Next(😬)
Next(😨)
Next(😡)
Next(🔴)
Error: Test
Next(😊)

---

retry

通过重新订阅Observable序列的方式来覆盖 Error 事件，直到没有 Error 事件为止。�了解更多

example("retry") {
    let disposeBag = DisposeBag()
    var count = 1

    let sequenceThatErrors = Observable<String>.create { observer in
        observer.onNext("🍎")
        observer.onNext("🍐")
        observer.onNext("🍊")

        if count == 1 {
            observer.onError(TestError.test)
            print("Error encountered")
            count += 1
        }
        observer.onNext("🐶")
        observer.onNext("🐱")
        observer.onNext("🐭")
        observer.onCompleted()

        return Disposables.create()
    }

    sequenceThatErrors
        .retry()
        .subscribe(onNext: { print($0) })
        .disposed(by: disposeBag)
}

Debug Area 输出：
--- retry example ---
🍎
🍐
🍊
Error encountered
🍎
🍐
🍊
🐶
🐱
🐭

---

retry(_:)

通过重新订阅Observable序列的方式来覆盖 Error 事件，直到重新订阅的次数达到maxAttemptCount的数量为止。�了解更多

example("retry maxAttemptCount") {
    let disposeBag = DisposeBag()
    var count = 1

    let sequenceThatErrors = Observable<String>.create { observer in
        observer.onNext("🍎")
        observer.onNext("🍐")
        observer.onNext("🍊")

        if count < 5 {
            observer.onError(TestError.test)
            print("Error encountered")
            count += 1
        }
        observer.onNext("🐶")
        observer.onNext("🐱")
        observer.onNext("🐭")
        observer.onCompleted()

        return Disposables.create()
    }

    sequenceThatErrors
        .retry(3)
        .subscribe(onNext: { print($0) })
        .disposed(by: disposeBag)
}

Debug Area 输出：
--- retry maxAttemptCount example ---
🍎
🍐
🍊
Error encountered
🍎
🍐
🍊
Error encountered
🍎
🍐
🍊
Error encountered

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