[英]How can i loop the observable sequence based on condition from each element?
我有一个序列,我需要根据每个元素的条件重复它。 例如,如果元素标有“失败”标志,我需要重新处理它。 我的问题是我找不到如何进行while-loop
操作。
TakeWhile
几乎是我所需要的,但它不会重演。
/*
* 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;
}
});
我建议将原始序列与一个新的observable合并,以便在失败时将对象输入。
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中更改对象状态通常被认为是不好的做法,因此您可能需要考虑创建转换:
loopSequence
.Where(item => item.Failed)
.Subscribe(item =>
{
try{
//Do stuff
retries.OnNext(new Item { ..., Failed = false });
} catch
{
retries.OnNext(new Item { ..., Failed = true });
}
});
你应该对这种模式非常小心,因为一个连续失败的项目会使你的程序执行成为一种无限循环。
您可以包装每个值并独立重试操作:
observableSequence
.SelectMany(item =>
Observable.Return(item)
.Select(x => //Do Stuff)
//Optional argument, omitting retries infinitely until
//success
.Retry(3)
)
.Subscribe(item => {
//Handle the results
});
(可选) Return
将IScheduler
作为其第二个参数,可以更改重试处理的顺序(递归与trampoline)。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.