所以我尝试使用onErrorReturn
返回我想要的结果,但是它将在之后完成流,如何捕获错误返回为Next并仍然继续流?
使用下面的代码,如果有错误,它将不会到达retryWhen
,如果我将其翻转,如果有错误,它将不会用retryWhen
重新订阅
fun process(): Observable<State> {
return publishSubject
.flatMap { intent ->
actAsRepo(intent) // Might return error
.map { State(data = it, error = null) }
}
.onErrorReturn { State(data = "", error = it) } // catch the error
.retryWhen { errorObs ->
errorObs.flatMap {
Observable.just(State.defaultState()) // continue subscribing
}
}
}
private fun actAsRepo(string: String): Observable<String> {
if (string.contains('A')) {
throw IllegalArgumentException("Contains A")
} else {
return Observable.just("Wrapped from repo: $string")
}
}
订户将是
viewModel.process().subscribe(this::render)
答案 0 :(得分:2)
onError是终端操作员。如果发生onError,它将在运算符之间传递。您可以使用onError-operator来捕获onError并提供后备功能。
在您的示例中,onError发生在flatMap的内部流中。 onError将向下游传播到onErrorReturn操作者。如果看一下实现,将看到将调用onErrorReturn lambda,结果将在onComplete之后通过onNext推送到下游
@Override
public void onError(Throwable t) {
T v;
try {
v = valueSupplier.apply(t);
} catch (Throwable e) {
Exceptions.throwIfFatal(e);
downstream.onError(new CompositeException(t, e));
return;
}
if (v == null) {
NullPointerException e = new NullPointerException("The supplied value is null");
e.initCause(t);
downstream.onError(e);
return;
}
downstream.onNext(v); // <--------
downstream.onComplete(); // <--------
}
由于以下原因,您的流完成了:#retryJavaDoc
如果操作员的上游是异步的,则立即发出onNext继之以onComplete信号可能会导致序列立即完成。类似地,如果在上游处于活动状态时此内部{@code ObservableSource}发出{@code onError}或{@code onComplete}信号,则序列将立即以相同信号终止。
将onErrorReturn放置在flatMap中的地图操作者之后。按照这种顺序,当inner-flatMap流onErrors时,您的流将无法完成。
当外部(源:publishSubject)和内部流(订阅)都完成时,flatMap运算符完成。在这种情况下,外部流(publishSubject)发出onNext,内部流将在通过onNext发送{State(data =“”,error = it)}之后完成。因此,流将保持打开状态。
interface ApiCall {
fun call(s: String): Observable<String>
}
class ApiCallImpl : ApiCall {
override fun call(s: String): Observable<String> {
// important: warp call into observable, that the exception is caught and emitted as onError downstream
return Observable.fromCallable {
if (s.contains('A')) {
throw IllegalArgumentException("Contains A")
} else {
s
}
}
}
}
data class State(val data: String, val err: Throwable? = null)
apiCallImpl.call将返回一个可延迟的可观察对象,这将在订阅时引发错误,而不是在可观察的汇编时间。
// no need for retryWhen here, except you want to catch onComplete from the publishSubject, but once the publishSubject completes no re-subscription will help you, because the publish-subject is terminated and onNext invocations will not be accepted anymore (see implementation).
fun process(): Observable<State> {
return publishSubject
.flatMap { intent ->
apiCallImpl.call(intent) // Might return error
.map { State(data = it, err = null) }
.onErrorReturn { State("", err = it) }
}
}
lateinit var publishSubject: PublishSubject<String>
lateinit var apiCallImpl: ApiCallImpl
@Before
fun init() {
publishSubject = PublishSubject.create()
apiCallImpl = ApiCallImpl()
}
@Test
fun myTest() {
val test = process().test()
publishSubject.onNext("test")
publishSubject.onNext("A")
publishSubject.onNext("test2")
test.assertNotComplete()
.assertNoErrors()
.assertValueCount(3)
.assertValueAt(0) {
assertThat(it).isEqualTo(State("test", null))
true
}
.assertValueAt(1) {
assertThat(it.data).isEmpty()
assertThat(it.err).isExactlyInstanceOf(IllegalArgumentException::class.java)
true
}
.assertValueAt(2) {
assertThat(it).isEqualTo(State("test2", null))
true
}
}
此替代方案的行为与第一种解决方案略有不同。 flatMap-Operator带有一个布尔值(delayError),这将导致吞入onError消息,直到源完成为止。当源完成时,将发出错误。
当异常没有用处且在出现时不得记录时,您可以使用delayError true
fun process(): Observable<State> {
return publishSubject
.flatMap({ intent ->
apiCallImpl.call(intent)
.map { State(data = it, err = null) }
}, true)
}
仅发出两个值。该错误不会转换为后备值。
@Test
fun myTest() {
val test = process().test()
publishSubject.onNext("test")
publishSubject.onNext("A")
publishSubject.onNext("test2")
test.assertNotComplete()
.assertNoErrors()
.assertValueAt(0) {
assertThat(it).isEqualTo(State("test", null))
true
}
.assertValueAt(1) {
assertThat(it).isEqualTo(State("test2", null))
true
}
.assertValueCount(2)
}
注意:我想您想在这种情况下使用switchMap而不是flatMap。