I see how to use .retry
directly, to resubscribe after an error, like this:
URLSession.shared.dataTaskPublisher(for:url)
.retry(3)
But that seems awfully simple-minded. What if I think that this error might go away if I wait awhile? I could insert a .delay
operator, but then the delay operates even if there is no error. And there doesn't seem to be a way to apply an operator conditionally (i.e. only when there's an error).
I see how I could work around this by writing a RetryWithDelay operator from scratch, and indeed such an operator has been written by third parties. But is there a way to say "delay if there's an error", purely using the operators we're given?
My thought was that I could use .catch
, because its function runs only if there is an error. But the function needs to return a publisher, and what publisher would we use? If we return somePublisher.delay(...)
followed by .retry
, we'd be applying .retry
to the wrong publisher, wouldn't we?
It was a topic of conversation on the Using Combine project repo a while back - the whole thread: https://github.com/heckj/swiftui-notes/issues/164.
The long and short was we made an example that I think does what you want, although it does use
catch
:This is referencing the a retry pattern I have in the book/online, which is basically what you describe (but wasn't what you asked about).
The person I was corresponding with on the issue provided a variant in that thread as an extension that might be interesting as well: