Add async initialization for Intl.message and an example

pkg/intl/example/basic/basic_example.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 provides a basic example of internationalization usage. It uses the
+ * local variant of all the facilities, meaning that libraries with the
+ * data for all the locales are directly imported by the program. More realistic
+ * examples might read the data from files or over the web, which uses the
+ * same APIs but requires different imports.
+ *
+ * This defines messages for an English locale directly in the program and
+ * has separate libraries that define German and Thai messages that say more or
+ * less the same thing, and prints the message with the date and time in it
+ * formatted appropriately for the locale.
+ */
+
+#library('intl_basic_example');
+// These can be replaced with package:intl/... references if using this in
+// a separate package.
+#import('../../date_format.dart');
+#import('../../date_symbol_data_local.dart');
+#import('../../intl.dart');
+#import('../../message_lookup_local.dart');
+#import('messages_all.dart');
+
+Function doThisWithTheOutput;
+
+void setup(Function program, Function output) {
+  // Before we use any messages or use date formatting for a locale we must
+  // call their initializtion messages, which are asynchronous, since they
+  // might be reading information from files or over the web. Since we are
+  // running here in local mode they will all complete immediately.
+  doThisWithTheOutput = output;
+  var germanDatesFuture = initializeDateFormatting('de_DE', null);
+  var thaiDatesFuture = initializeDateFormatting('th_TH', null);
+  var germanMessagesFuture = initializeMessages('de_DE');
+  var thaiMessagesFuture = initializeMessages('th_TH');
+  Futures.wait([germanDatesFuture, thaiDatesFuture, germanMessagesFuture,
+                thaiMessagesFuture]).then(program);
+}
+
+// Because the initialization messages return futures we split out the main
+// part of our program into a separate function that runs once all the
+// futures have completed. We are passed the collection of futures, but we
+// don't need to use them, so ignore the parameter.
+runProgram(List<Future> _) {
+  var aDate = new Date.fromMillisecondsSinceEpoch(0, true);
+  var de = new Intl('de_DE');
+  var th = new Intl('th_TH');
+  // This defines a message that can be internationalized. It is written as a
+  // function that returns the result of an Intl.message call. The primary
+  // parameter is a string that may use interpolation.
+  runAt(time, date) =>
+      Intl.message('Ran at $time on $date', name: 'runAt', args: [time, date]);
+  printForLocale(aDate, new Intl(), runAt);
+  printForLocale(aDate, de, runAt);
+  printForLocale(aDate, th, runAt);
+}
+
+printForLocale(aDate, intl, operation) {
+  var hmsFormat = intl.date().add_Hms();
+  var dayFormat = intl.date().add_yMMMMEEEEd();
+  var time = hmsFormat.format(aDate);
+  var day = dayFormat.format(aDate);
+  Intl.withLocale(intl.locale, () { doThisWithTheOutput(operation(time,day));});
+}