I’m having some trouble with a Promise stored in a member variable, where the
’then’ block attached to the promise calls code that ends up clearing that
variable. This then triggers a kj exception that a Promise is being destructed
while it’s being processed. I understand why this is an error, but I can’t
figure out how else to clean up that variable.
The situation is like:
std::optional<Promise<void>> _promise; // This is a data member of my
class
// In a method of my class:
_promise = something.then([=] {
…do the work…
_promise.clear(); // <— boom
});
How can I make sure _promise is cleared after its handler completes?
I need a specific reference to the promise — I can’t just shove it into a
TaskSet — because I have code in other methods that clears _promise when it
decides that it’s no longer needed. (Specifically, this is an idle timer, so
when an action occurs it needs to clear the timer.)
I can think of a few ways to fix this, but they feel like hacks. I get the
feeling this is a situation that comes up in various circumstances — a promise
whose resolution has to clear the Promise variable. Is there a more established
best practice for handling it?
—Jens
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