CatchError

從一個錯誤事件中恢復，將錯誤事件替換成一個備選序列

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

sequenceThatFails.catchError { (error) -> Observable<String> in
        print("error: ", error)
        return recoverySequence
    }.subscribe
 
(onNext: {
        print($0)
    }).disposed(by: disposeBag)

sequenceThatFails.onNext("A")
sequenceThatFails.onNext("B")
sequenceThatFails.onNext("C")
sequenceThatFails.onNext("D")
sequenceThatFails.onError(HHError(name: "test"))
recoverySequence.onNext("1")
recoverySequence.onNext("2")

/*
 A
 B
 C
 D
 error:  __lldb_expr_144.HHError
 1
 2
 */
 

CatchErrorJustReturn

會將 error 事件替換成其他的一個元素，然後結束該序列

sequenceThatFails.catchErrorJustReturn("666")
    .subscribe(onNext: {
    print($0)
}).disposed(by: disposeBag)

sequenceThatFails.onNext("1")
sequenceThatFails.onNext("2")
sequenceThatFails.onNext("3")
sequenceThatFails.onError(HHError(name: "test"
 
))

/*
666
 */

Retry

如果源 Observable 產生一個錯誤事件，重新對它進行訂閱，希望它不會再次產生錯誤

var count = 1
let canErrorSequence = Observable<String>.create { (observer) -> Disposable in
    observer.onNext("A")
    observer.onNext("B")
    observer.onNext("C")

    if count == 1 {
        observer.onError(HHError.init(name: "text"))
        print("Error encountered")
        count += 1
    }

    observer.onNext("1")
    observer.onNext("2")
    observer.onNext("3")
    observer.onCompleted()

    return Disposables.create()

}

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

/*
 A
 B
 C
 Error encountered
 A
 B
 C
 1
 2
 3
 */

Debug

將 debug 除錯操作符新增到一個鏈式步驟當中，這樣系統就能將所有的訂閱者、事件、和處理等詳細資訊打印出來，方便我們開發除錯

/// debug() 不傳引數 列印當前方法名
Observable.of("A", "B", "C", "D", "E", "F", "G").debug().subscribe(onNext: {
    print($0)
}).disposed(by: disposeBag)

/// debug() 傳引數 列印引數名
Observable.of("A", "B", "C", "D", "E", "F", "G").debug("除錯:").subscribe(onNext: {
    print($0)
}).disposed(by: disposeBag)