| // Copyright 2009 The Closure Library Authors. All Rights Reserved. |
| // |
| // 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. |
| |
| /** |
| * @fileoverview Useful compiler idioms. |
| * |
| * @author johnlenz@google.com (John Lenz) |
| */ |
| |
| goog.provide('goog.reflect'); |
| |
| |
| /** |
| * Syntax for object literal casts. |
| * @see http://go/jscompiler-renaming |
| * @see https://goo.gl/CRs09P |
| * |
| * Use this if you have an object literal whose keys need to have the same names |
| * as the properties of some class even after they are renamed by the compiler. |
| * |
| * @param {!Function} type Type to cast to. |
| * @param {Object} object Object literal to cast. |
| * @return {Object} The object literal. |
| */ |
| goog.reflect.object = function(type, object) { |
| return object; |
| }; |
| |
| /** |
| * Syntax for renaming property strings. |
| * @see http://go/jscompiler-renaming |
| * @see https://goo.gl/CRs09P |
| * |
| * Use this if you have an need to access a property as a string, but want |
| * to also have the property renamed by the compiler. In contrast to |
| * goog.reflect.object, this method takes an instance of an object. |
| * |
| * Properties must be simple names (not qualified names). |
| * |
| * @param {string} prop Name of the property |
| * @param {!Object} object Instance of the object whose type will be used |
| * for renaming |
| * @return {string} The renamed property. |
| */ |
| goog.reflect.objectProperty = function(prop, object) { |
| return prop; |
| }; |
| |
| /** |
| * To assert to the compiler that an operation is needed when it would |
| * otherwise be stripped. For example: |
| * <code> |
| * // Force a layout |
| * goog.reflect.sinkValue(dialog.offsetHeight); |
| * </code> |
| * @param {T} x |
| * @return {T} |
| * @template T |
| */ |
| goog.reflect.sinkValue = function(x) { |
| goog.reflect.sinkValue[' '](x); |
| return x; |
| }; |
| |
| |
| /** |
| * The compiler should optimize this function away iff no one ever uses |
| * goog.reflect.sinkValue. |
| */ |
| goog.reflect.sinkValue[' '] = goog.nullFunction; |
| |
| |
| /** |
| * Check if a property can be accessed without throwing an exception. |
| * @param {Object} obj The owner of the property. |
| * @param {string} prop The property name. |
| * @return {boolean} Whether the property is accessible. Will also return true |
| * if obj is null. |
| */ |
| goog.reflect.canAccessProperty = function(obj, prop) { |
| |
| try { |
| goog.reflect.sinkValue(obj[prop]); |
| return true; |
| } catch (e) { |
| } |
| return false; |
| }; |
| |
| |
| /** |
| * Retrieves a value from a cache given a key. The compiler provides special |
| * consideration for this call such that it is generally considered side-effect |
| * free. However, if the {@code opt_keyFn} or {@code valueFn} have side-effects |
| * then the entire call is considered to have side-effects. |
| * |
| * Conventionally storing the value on the cache would be considered a |
| * side-effect and preclude unused calls from being pruned, ie. even if |
| * the value was never used, it would still always be stored in the cache. |
| * |
| * Providing a side-effect free {@code valueFn} and {@code opt_keyFn} |
| * allows unused calls to {@code goog.reflect.cache} to be pruned. |
| * |
| * @param {!Object<K, V>} cacheObj The object that contains the cached values. |
| * @param {?} key The key to lookup in the cache. If it is not string or number |
| * then a {@code opt_keyFn} should be provided. The key is also used as the |
| * parameter to the {@code valueFn}. |
| * @param {function(?):V} valueFn The value provider to use to calculate the |
| * value to store in the cache. This function should be side-effect free |
| * to take advantage of the optimization. |
| * @param {function(?):K=} opt_keyFn The key provider to determine the cache |
| * map key. This should be used if the given key is not a string or number. |
| * If not provided then the given key is used. This function should be |
| * side-effect free to take advantage of the optimization. |
| * @return {V} The cached or calculated value. |
| * @template K |
| * @template V |
| */ |
| goog.reflect.cache = function(cacheObj, key, valueFn, opt_keyFn) { |
| var storedKey = opt_keyFn ? opt_keyFn(key) : key; |
| |
| if (Object.prototype.hasOwnProperty.call(cacheObj, storedKey)) { |
| return cacheObj[storedKey]; |
| } |
| |
| return (cacheObj[storedKey] = valueFn(key)); |
| }; |