Async initialization for DateFormat

pkg/intl/lib/file_data_reader.dart

+// Copyright (c) 2012, 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.
+
+/**
+ * This contains a reader that accesses data from local files, so it can't
+ * be run in the browser.
+ */
+
+#library('file_data_reader');
+
+#import('dart:io');
+#import('intl_helpers.dart');
+
+class FileDataReader implements LocaleDataReader {
+
+  /// The base path from which we will read data.
+  String path;
+
+  FileDataReader(this.path);
+
+  /// Read the locale data found for [locale] on our [path].
+  Future read(String locale) {
+    var file = new File('$path$locale.json');
+    return file.readAsText();
+  }
+}