[added] NativeHistory -wip

Author: mjackson

modules/NativeHistory.js

@@ -0,0 +1,69 @@
+import { AsyncStorage, PropTypes } from 'react-native';
+import MemoryHistory from './MemoryHistory';
+import Location from './Location';
+
+var { bool, string } = PropTypes;
+
+function encodeState(state) {
+  return JSON.stringify(state);
+}
+
+function decodeState(string) {
+  var state;
+  try {
+    state = JSON.parse(string);
+  } catch (error) {
+    // Invalid JSON in AsyncStorage for some reason. Ignore it.
+    state = {};
+  }
+
+  // Make sure we have a real Location.
+  if (state && state.location) {
+    var { location } = state;
+    state.location = new Location(location.path, location.query, location.navigationType);
+  }
+
+  return state;
+}
+
+/**
+ * A history implementation for React Native environments that
+ * supports persistence across the application lifecycle using
+ * the AsyncStorage module.
+ */
+class NativeHistory extends MemoryHistory {
+
+  static propTypes = Object.assign({}, MemoryHistory.propTypes, {
+    storageKey: string.isRequired,
+    autoSave: bool.isRequired
+  });
+
+  static defaultProps = Object.assign({}, MemoryHistory.defaultProps, {
+    storageKey: '@ReactRouterNativeHistory',
+    autoSave: true
+  });
+
+  static childContextTypes = Object.assign({}, MemoryHistory.childContextTypes);
+  
+  componentWillMount() {
+    AsyncStorage.getItem(this.props.storageKey, (error, value) => {
+      if (error) {
+        throw error; // TODO: Keep this around in state?
+      } else {
+        this.setState(decodeState(value));
+      }
+    });
+  }
+
+  componentDidUpdate() {
+    if (this.props.autoSave)
+      this.saveToAsyncStorage();
+  }
+
+  saveToAsyncStorage(callback) {
+    AsyncStorage.setItem(this.props.storageKey, encodeState(this.state), callback);
+  }
+
+}
+
+export default NativeHistory;