blob: 9d3f0e29f677582557f7a5a3ed7fd03bc3333400 [file] [log] [blame]
// Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
library when.example.read_json_file;
import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'package:when/when.dart';
/// Reads and decodes JSON from [path] asynchronously.
/// If [path] does not exist, returns the result of calling [onAbsent].
Future readJsonFile(String path, {onAbsent()}) => _readJsonFile(
path, onAbsent, (file) => file.exists(), (file) => file.readAsString());
/// Reads and decodes JSON from [path] synchronously.
/// If [path] does not exist, returns the result of calling [onAbsent].
dynamic readJsonFileSync(String path, {onAbsent()}) => _readJsonFile(
path, onAbsent, (file) => file.existsSync(),
(file) => file.readAsStringSync());
_readJsonFile(String path, onAbsent(), exists(File file), read(File file)) {
var file = new File(path);
return when(
() => exists(file),
onSuccess: (doesExist) => doesExist ?
when(() => read(file), onSuccess: JSON.decode) :
main() {
var syncJson = readJsonFileSync('foo.json', onAbsent: () => {'foo': 'bar'});
print('Sync json: $syncJson');
readJsonFile('foo.json', onAbsent: () => {'foo': 'bar'}).then((asyncJson) {
print('Async json: $asyncJson');