aa092a4111
git-subtree-dir: packages/poll git-subtree-mainline:a5f5661650git-subtree-split:14637ac137
42 lines
No EOL
1.6 KiB
Markdown
42 lines
No EOL
1.6 KiB
Markdown
# poll
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[](https://pub.dartlang.org/packages/angel_poll)
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[](https://travis-ci.org/angel-dart/poll)
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`package:angel_client` support for "realtime" interactions with Angel via long polling.
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Angel supports [WebSockets](https://github.com/angel-dart/websocket) on the server and client, which
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makes it very straightforward to implement realtime collections. However, not every user's browser
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supports WebSockets. In such a case, applications might *gracefully degrade* to long-polling
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the server for changes.
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A `PollingService` wraps a client-side `Service` (typically a REST-based one), and calls its
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`index` method at a regular interval. After indexing, the `PollingService` performs a diff
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and identifies whether items have been created, modified, or removed. The updates are sent out
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through `onCreated`, `onModified`, etc., effectively managing a real-time collection of data.
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A common use-case would be passing this service to `ServiceList`, a class that manages the state
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of a collection managed in real-time.
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```dart
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import 'package:angel_client/io.dart';
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import 'package:angel_poll/angel_poll.dart';
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main() {
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var app = new Rest('http://localhost:3000');
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var todos = new ServiceList(
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new PollingService(
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// Typically, you'll pass a REST-based service instance here.
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app.service('api/todos'),
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// `index` called every 5 seconds
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const Duration(seconds: 5),
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),
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);
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todos.onChange.listen((_) {
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// Something happened here.
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// Maybe an item was created, modified, etc.
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});
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}
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``` |