[英]How can i loop the observable sequence based on condition from each element?
我有一個序列,我需要根據每個元素的條件重復它。 例如,如果元素標有“失敗”標志,我需要重新處理它。 我的問題是我找不到如何進行while-loop
操作。
TakeWhile
幾乎是我所需要的,但它不會重演。
/*
* The following lines are just an example to comprehend the idea
*/
var observableSequence = sequence.ToObservable();
observableSequence
//This ´DoWhile´ did not worked because does not accept each element as argument
//and sequence at this point is not the same as `observableSequence`
.DoWhile(() => sequence.Any(item => !item.Failed))
.Where(item => item.Failed == true) //OK here i could put another condition for limited retries...
.Subscribe(item => {
try{
//Do stuff...
//. . .
item.Failed = false;
} catch
{
item.Failed = true;
}
});
我建議將原始序列與一個新的observable合並,以便在失敗時將對象輸入。
var retries = new ReplaySubject<Foo>();
var loopSequence = sequence.ToObservable().Merge(retries);
loopSequence
.Where(item => item.Failed)
.Subscribe(item =>
{
try{
//Do stuff
item.Failed = false;
} catch
{
item.Failed = true;
}
retries.OnNext(item);
});
在observables中更改對象狀態通常被認為是不好的做法,因此您可能需要考慮創建轉換:
loopSequence
.Where(item => item.Failed)
.Subscribe(item =>
{
try{
//Do stuff
retries.OnNext(new Item { ..., Failed = false });
} catch
{
retries.OnNext(new Item { ..., Failed = true });
}
});
你應該對這種模式非常小心,因為一個連續失敗的項目會使你的程序執行成為一種無限循環。
您可以包裝每個值並獨立重試操作:
observableSequence
.SelectMany(item =>
Observable.Return(item)
.Select(x => //Do Stuff)
//Optional argument, omitting retries infinitely until
//success
.Retry(3)
)
.Subscribe(item => {
//Handle the results
});
(可選) Return
將IScheduler
作為其第二個參數,可以更改重試處理的順序(遞歸與trampoline)。
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