Promise feature for dartlang, reference from javascript Promise.
| Feature | Dart | ES Promise |
|---|---|---|
| then | promise.then | promise.then |
| catch | promise.catchError(catch is a keyword in dart, not allowed as a method, use catchError instead) |
promise.catch |
| finally | promise.always(finally is a keyword in dart, not allowed as a method, use always instead) |
promise.finally |
| resolve | Promise.resolve | Promise.resolve |
| reject | Promise.reject | Promise.reject |
| race | Promise.race | Promise.race |
| all | Promise.all | Promise.all |
import 'dart:async';
import './lib/promise.dart';
Promise delay(int seconds, String val) {
return Promise((resolve, _) {
Timer(Duration(seconds: seconds), () {
resolve(val);
});
});
}
void main() {
// case 1
Promise((resolve, reject) {
Timer(Duration(seconds: 2), () {
resolve('Case1: resolved');
});
}).then(print);
// case 2
Promise((resolve, reject) {
Timer(Duration(seconds: 2), () {
reject('Case2: rejected');
});
}).then(null, print);
// case 3
Promise.all([delay(2, 'A'), delay(1, 'B'), delay(3, 'C')]).then((val) {
print('Case3: $val');
});
// case 4
Promise.race([delay(2, 'A'), delay(1, 'B'), delay(3, 'C')]).then((val) {
print('Case4: $val');
});
// case 5
Promise.reject('Case5').catchError((err) {
print('Case5: Error');
}).always(() => print('Case5: always run'));
// case 6
Promise.resolve('Case6').then((val) {
return Promise.reject('$val: nested');
}).catchError(print);
// case 7
Promise((resolve, reject) {
resolve('Case7: run first, ignore next reslove or reject');
reject('Case7: reject run?');
}).then(print);
}