前言
本节中主要介绍错误处理
// 定义一个错误
public enum TestError : Error {
case test
}
Error Handling Operators
-
catchErrorJustReturn
遇到错误时限抛出预设的next事件，然后结束即Complete,但是不会发出错误事件
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)
}
// 控制台打印的结果：
--- catchErrorJustReturn example ---
next(😬)
next(😨)
next(😡)
next(🔴)
next(😊)
completed
-
catchError
遇到错误会进入走闭包的分支，然后切换到闭包中返回的预先设置的其他的观察序列
example("catchError") {
let disposeBag = DisposeBag()
let sequenceThatFails = PublishSubject<String>()
let recoverySequence = PublishSubject<String>()
sequenceThatFails
.catchError {
print("Error:", $0)
return recoverySequence
}
.subscribe { print($0) }
.disposed(by: disposeBag)
sequenceThatFails.onNext("😬")
sequenceThatFails.onNext("😨")
sequenceThatFails.onNext("😡")
sequenceThatFails.onNext("🔴")
sequenceThatFails.onError(TestError.test)
recoverySequence.onNext("😊")
}
// 控制台打印的结果：
--- catchError example ---
next(😬)
next(😨)
next(😡)
next(🔴)
Error: test
next(😊)
-
retry
遇到错误以后，会尝试通过再次订阅序列，如果在遇到错误就再订阅，如此周而复始
官方示例程序
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)
}
// 控制台打印的结果：
--- retry example ---
🍎
🍐
🍊
Error encountered
🍎
🍐
🍊
🐶
🐱
🐭
为了展示周而复始的过程，我修改了一下代码
example("retry") {
let disposeBag = DisposeBag()
var count = 1
let sequenceThatErrors = Observable<String>.create { observer in
observer.onNext("🍎")
observer.onNext("🍐")
observer.onNext("🍊")
/***** 在增加一次错误，看其如何处理 ***/
if count == 2{
observer.onError(TestError.test)
print("Error encountered")
count += 1
}
/*********************************/
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)
}
// 控制台打印的结果：
--- retry example ---
🍎
🍐
🍊
Error encountered
🍎
🍐
🍊
Error encountered*****
🍎
🍐
🍊
🐶
🐱
🐭
-
retry(_:)
和retry的功能一直，参数是限定了重复订阅的次数
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)
}
// 控制台打印的结果：
--- retry maxAttemptCount example ---
🍎
🍐
🍊
Error encountered
🍎
🍐
🍊
Error encountered
🍎
🍐
🍊
Error encountered
``
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