user/src/com/google/gwt/user/client/impl/EventMap.java

/*
 * Copyright 2013 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.user.client.impl;

import com.google.gwt.core.client.JavaScriptObject;

/**
 * A simple helper class to abstract event maps.
 */
class EventMap extends JavaScriptObject {

  protected EventMap() { /* Mandatory constructor for JSO */}

  /**
   * Merges the key-value pairs from the parameter into this object. If a key already exists, then
   * it will be overridden by the new value.
   */
  public final void merge(JavaScriptObject eventMap) {
    foreach(eventMap, copyTo(this));
  }

  /**
   * Returns a function that copies the passed key-value to target object.
   */
  private static native JavaScriptObject copyTo(EventMap target) /*-{
    return function(key, value) { target[key] = value; };
  }-*/;

  /**
   * Executes a provided function over the key-value pairs of the map object.
   */
  static native void foreach(JavaScriptObject map, JavaScriptObject fn) /*-{
    for (var e in map) {
      if (map.hasOwnProperty(e)) {
        fn(e, map[e]);
      }
    }
  }-*/;
}