async_field

Description:

async field

async_field #











Async fields that can be stored or fetched from any source (databases, web services, local storage or other thread/isolate), with observable values, caches and stale versions.
Usage #
A simple usage example:
import 'dart:convert' as convert;
import 'dart:io';

import 'package:async_field/async_field.dart';

void main() async {
// The fields storage:
var storage = AsyncStorage();

// Get field 'btc_usd',
var field = storage.getField<double>('btc_usd')
..defaultValue = double.nan // default value (before fetch).
..withFetcher(_fetchBtcUsd) // the field fetcher.
..onChange.listen((field) => print('onChange> $field')); // change listener.

print('BTX-USD: $field');
print('field.info: ${field.info}');

// Get the field value:
var btcUsd = await field.get();

print('field.get(): $btcUsd');

print('BTX-USD: $field');
print('field.info: ${field.info}');
}

/// Function that fetches the BTS-USD price.
Future<double> _fetchBtcUsd(AsyncField<double> field) async {
return _getURL('https://api.coindesk.com/v1/bpi/currentprice.json')
.resolveMapped((body) {
var json = convert.json.decode(body) as Map<String, dynamic>;
var rate = json['bpi']['USD']['rate_float'];
return double.parse('$rate');
});
}

/// Simple HTTP get URL function.
Future<String> _getURL(String url) async {
var uri = Uri.parse(url);
var httpClient = HttpClient();

var response =
await httpClient.getUrl(uri).then((request) => request.close());

var data = await response.transform(convert.Utf8Decoder()).toList();
var body = data.join();
return body;
}
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OUTPUT:
BTX-USD: NaN
field.info: { "id": "btc_usd" , "storage": 1 }
field.get(): 34498.9417
BTX-USD: 34498.9417
field.info: { "value": 34498.9417 , "id": "btc_usd" , "valueTime": 1624846823650 , "storage": 1 }
onChange> 34498.9417
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Source #
The official source code is hosted @ GitHub:

https://github.com/eneural-net/async_field

Features and bugs #
Please file feature requests and bugs at the issue tracker.
Contribution #
Any help from the open-source community is always welcome and needed:

Found an issue?

Please fill a bug report with details.


Wish a feature?

Open a feature request with use cases.


Are you using and liking the project?

Promote the project: create an article, do a post or make a donation.


Are you a developer?

Fix a bug and send a pull request.
Implement a new feature.
Improve the Unit Tests.


Have you already helped in any way?

Many thanks from me, the contributors and everybody that uses this project!



If you donate 1 hour of your time, you can contribute a lot,
because others will do the same, just be part and start with your 1 hour.
Author #
Graciliano M. Passos: gmpassos@GitHub.
License #
Apache License - Version 2.0