1 /**
  2  * Copyright (C) 2010-2014 KO GmbH <copyright@kogmbh.com>
  3  *
  4  * @licstart
  5  * This file is part of WebODF.
  6  *
  7  * WebODF is free software: you can redistribute it and/or modify it
  8  * under the terms of the GNU Affero General Public License (GNU AGPL)
  9  * as published by the Free Software Foundation, either version 3 of
 10  * the License, or (at your option) any later version.
 11  *
 12  * WebODF is distributed in the hope that it will be useful, but
 13  * WITHOUT ANY WARRANTY; without even the implied warranty of
 14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15  * GNU Affero General Public License for more details.
 16  *
 17  * You should have received a copy of the GNU Affero General Public License
 18  * along with WebODF.  If not, see <http://www.gnu.org/licenses/>.
 19  * @licend
 20  *
 21  * @source: http://www.webodf.org/
 22  * @source: https://github.com/kogmbh/WebODF/
 23  */
 24 
 25 /*global core*/
 26 
 27 // TODO Apparently newer closure compilers do a better job with generics
 28 
 29 /**
 30  * Lazily loaded property. The value is loaded using the valueLoader and cached
 31  * the first time it's requested. Subsequent requests will return the cached value.
 32  * Calling reset will clear the cached value, causing the next value request
 33  * to load a new value via the valueLoader.
 34  *
 35  * @constructor
 36  * @template T
 37  * @param {!function():Object} valueLoader Property value loader
 38  */
 39 core.LazyProperty = function (valueLoader) {
 40     "use strict";
 41     var cachedValue,
 42         valueLoaded = false;
 43 
 44     /**
 45      * @return {T}
 46      */
 47     this.value = function() {
 48         if (!valueLoaded) {
 49             cachedValue = valueLoader();
 50             valueLoaded = true;
 51         }
 52         return cachedValue;
 53     };
 54 
 55     /**
 56      * @return {undefined}
 57      */
 58     this.reset = function() {
 59         valueLoaded = false;
 60     };
 61 };
 62