(This answer applies to Polymer.dart.)
The observe
package includes a wrapper for single observable values: ObservableBox
.
import 'package:observe/observe.dart';
import 'dart:async';
void main() {
ObservableBox myValue = new ObservableBox('hello');
myValue.changes.listen((List<ChangeRecord> records) {
PropertyChangeRecord record = records[0] as PropertyChangeRecord;
print('${record.field} changed, it is now ${myValue.value}');
});
new Timer.periodic(const Duration(seconds: 1), (t) {
myValue.value = new DateTime.now();
});
}
There is no way to observe a top-level or function-scope single string, boolean, int, or double without using ObservableBox.
If the string, boolean, int, or double is a field of a class, you can use ObservableMixin
and the @observable
annotation.
class Foo extends Object with ObservableMixin {
@observable String bar = '';
}
You can then get notified when an instance of Foo changes:
foo.changes.listen((List<ChangeRecord> records) {
// ...
});