Created
September 4, 2024 15:54
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Dart firstThatResolves
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| import 'dart:async'; | |
| extension FutureX<T> on Future<T> { | |
| /// This function accepts two functions returning a future, | |
| /// and returns whichever function resolves successfully first. | |
| /// | |
| /// Can be used in case one of the functions may fail | |
| /// even under normal circumstances as long as the other succeeds | |
| /// (so at least one of them should succeed). | |
| /// | |
| /// If both functions return an error, this static method will | |
| /// use the second error. | |
| static Future<T> firstThatResolves<T>( | |
| Future<T> Function() a, | |
| Future<T> Function() b, | |
| ) { | |
| final completer = Completer<T>(); | |
| var aCompleted = false; | |
| var bCompleted = false; | |
| a().then((t) { | |
| aCompleted = true; | |
| if (bCompleted) return; | |
| completer.complete(t); | |
| }).catchError((Object e, StackTrace st) { | |
| aCompleted = true; | |
| if (bCompleted && completer.isCompleted) return; | |
| completer.completeError(e, st); | |
| }); | |
| b().then((t) { | |
| bCompleted = true; | |
| if (aCompleted) return; | |
| completer.complete(t); | |
| }).catchError((Object e, StackTrace st) { | |
| bCompleted = true; | |
| if (aCompleted) return; | |
| completer.completeError(e, st); | |
| }); | |
| return completer.future; | |
| } | |
| } |
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