Completer abstract class
A way to produce Future objects and to complete them later with a value or error.
Most of the time, the simplest way to create a future is to just use one of the Future constructors to capture the result of a single asynchronous computation:
new Future(() { doSomething(); return result; });
or, if the future represents the result of a sequence of asynchronous computations, they can be chained using Future.then or similar functions on Future:
Future doStuff(){ return someAsyncOperation().then((result) { return someOtherAsyncOperation(result); }); }
If you do need to create a Future from scratch — for example, when you're converting a callback-based API into a Future-based one — you can use a Completer as follows:
class AsyncOperation { Completer _completer = new Completer(); Future<T> doOperation() { _startOperation(); return _completer.future; // Send future object back to client. } // Something calls this when the value is ready. void _finishOperation(T result) { _completer.complete(result); } // If something goes wrong, call this. void _errorHappened(error) { _completer.completeError(error); } }
Constructors
- Completer() factory
-
Creates a new completer.
- Completer.sync() factory
-
Completes the future synchronously.
Properties
- future → Future<T> read-only
-
The future that will contain the result provided to this completer.
- isCompleted → bool read-only
-
Whether the future has been completed.
- hashCode → int read-only, inherited
-
The hash code for this object.
- runtimeType → Type read-only, inherited
-
A representation of the runtime type of the object.
Operators
- operator ==(
other) → bool inherited -
The equality operator.
Methods
- complete(
[value ]) → void -
Completes future with the supplied values.
- completeError(
Object error, [ StackTrace stackTrace ]) → void -
Complete future with an error.
- noSuchMethod(
Invocation invocation) → dynamic inherited -
Invoked when a non-existent method or property is accessed.
- toString(
) → String inherited -
Returns a string representation of this object.
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/1.24.3/dart-async/Completer-class.html