pkg/polymer/lib/deserialize.dart

// Copyright (c) 2013, 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 polymer.deserialize;

import 'dart:convert' show JSON;
import 'dart:mirrors' show reflect, TypeMirror;

final _typeHandlers = () {
  // TODO(jmesserly): switch to map and symbol literal form when supported.
  var m = new Map();
  m[const Symbol('dart.core.String')] = (x, _) => x;
  m[const Symbol('dart.core.Null')] = (x, _) => x;
  m[const Symbol('dart.core.DateTime')] = (x, _) {
    // TODO(jmesserly): shouldn't need to try-catch here
    // See: https://code.google.com/p/dart/issues/detail?id=1878
    try {
      return DateTime.parse(x);
    } catch (e) {
      return new DateTime.now();
    }
  };
  m[const Symbol('dart.core.bool')] = (x, _) => x != 'false';
  m[const Symbol('dart.core.int')] =
      (x, def) => int.parse(x, onError: (_) => def);
  m[const Symbol('dart.core.double')] =
      (x, def) => double.parse(x, (_) => def);
  return m;
}();

/**
 * Convert representation of [value] based on type of [defaultValue].
 */
Object deserializeValue(String value, Object defaultValue, TypeMirror type) {
  var handler = _typeHandlers[type.qualifiedName];
  if (handler != null) return handler(value, defaultValue);

  try {
    // If the string is an object, we can parse is with the JSON library.
    // include convenience replace for single-quotes. If the author omits
    // quotes altogether, parse will fail.
    return JSON.decode(value.replaceAll("'", '"'));

    // TODO(jmesserly): deserialized JSON is not assignable to most objects in
    // Dart. We should attempt to convert it appropriately.
  } catch(e) {
    // The object isn't valid JSON, return the raw value
    return value;
  }
}