Perform an async operation repeatedly until it returns false
.
Runs f
repeatedly, starting the next iteration only when the Future
returned by f
completes to true
. Returns a Future that completes once
f
returns false
.
The return values of all Futures are discarded. Any errors will cause the iteration to stop and will be piped through the returned Future.
The function f
may return either a bool or a Future that completes to
a bool. If it returns a non-Future, iteration continues immediately.
Otherwise it waits for the returned Future to complete.
Source
static Future doWhile(f()) {
_Future doneSignal = new _Future();
var nextIteration;
// Bind this callback explicitly so that each iteration isn't bound in the
// context of all the previous iterations' callbacks.
nextIteration = Zone.current.bindUnaryCallback((bool keepGoing) {
if (keepGoing) {
new Future.sync(f).then(nextIteration,
onError: doneSignal._completeError);
} else {
doneSignal._complete(null);
}
}, runGuarded: true);
nextIteration(true);
return doneSignal;
}