observer-proxy.js 10 KB

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  1. /**
  2. * @license
  3. * Copyright 2021 Google Inc.
  4. *
  5. * Permission is hereby granted, free of charge, to any person obtaining a copy
  6. * of this software and associated documentation files (the "Software"), to deal
  7. * in the Software without restriction, including without limitation the rights
  8. * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  9. * copies of the Software, and to permit persons to whom the Software is
  10. * furnished to do so, subject to the following conditions:
  11. *
  12. * The above copyright notice and this permission notice shall be included in
  13. * all copies or substantial portions of the Software.
  14. *
  15. * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16. * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17. * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18. * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19. * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20. * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  21. * THE SOFTWARE.
  22. */
  23. import { __extends, __read, __spreadArray, __values } from "tslib";
  24. import { getDescriptor } from './observer';
  25. /**
  26. * Mixin to add `MDCObserver` functionality to an optional base class.
  27. *
  28. * @deprecated Prefer MDCObserverFoundation for stricter closure compliance.
  29. * @template C Optional base class constructor type.
  30. * @param baseClass - Optional base class.
  31. * @return A class that extends the optional base class with `MDCObserver`
  32. * functionality.
  33. */
  34. export function mdcObserver(baseClass) {
  35. var _a, _b;
  36. if (baseClass === void 0) { baseClass = /** @class */ (function () {
  37. function class_1() {
  38. }
  39. return class_1;
  40. }()); }
  41. var unobserves = Symbol();
  42. return _b = /** @class */ (function (_super) {
  43. __extends(MDCObserver, _super);
  44. function MDCObserver() {
  45. var _this = _super !== null && _super.apply(this, arguments) || this;
  46. _this[_a] = [];
  47. return _this;
  48. }
  49. MDCObserver.prototype.observe = function (target, observers) {
  50. var e_1, _b;
  51. var _this = this;
  52. var cleanup = [];
  53. try {
  54. for (var _c = __values(Object.keys(observers)), _d = _c.next(); !_d.done; _d = _c.next()) {
  55. var property = _d.value;
  56. var observer = observers[property].bind(this);
  57. cleanup.push(observeProperty(target, property, observer));
  58. }
  59. }
  60. catch (e_1_1) { e_1 = { error: e_1_1 }; }
  61. finally {
  62. try {
  63. if (_d && !_d.done && (_b = _c.return)) _b.call(_c);
  64. }
  65. finally { if (e_1) throw e_1.error; }
  66. }
  67. var unobserve = function () {
  68. var e_2, _b;
  69. try {
  70. for (var cleanup_1 = __values(cleanup), cleanup_1_1 = cleanup_1.next(); !cleanup_1_1.done; cleanup_1_1 = cleanup_1.next()) {
  71. var cleanupFn = cleanup_1_1.value;
  72. cleanupFn();
  73. }
  74. }
  75. catch (e_2_1) { e_2 = { error: e_2_1 }; }
  76. finally {
  77. try {
  78. if (cleanup_1_1 && !cleanup_1_1.done && (_b = cleanup_1.return)) _b.call(cleanup_1);
  79. }
  80. finally { if (e_2) throw e_2.error; }
  81. }
  82. var index = _this[unobserves].indexOf(unobserve);
  83. if (index > -1) {
  84. _this[unobserves].splice(index, 1);
  85. }
  86. };
  87. this[unobserves].push(unobserve);
  88. return unobserve;
  89. };
  90. MDCObserver.prototype.setObserversEnabled = function (target, enabled) {
  91. setObserversEnabled(target, enabled);
  92. };
  93. MDCObserver.prototype.unobserve = function () {
  94. var e_3, _b;
  95. try {
  96. // Iterate over a copy since unobserve() will remove themselves from the
  97. // array
  98. for (var _c = __values(__spreadArray([], __read(this[unobserves]))), _d = _c.next(); !_d.done; _d = _c.next()) {
  99. var unobserve = _d.value;
  100. unobserve();
  101. }
  102. }
  103. catch (e_3_1) { e_3 = { error: e_3_1 }; }
  104. finally {
  105. try {
  106. if (_d && !_d.done && (_b = _c.return)) _b.call(_c);
  107. }
  108. finally { if (e_3) throw e_3.error; }
  109. }
  110. };
  111. return MDCObserver;
  112. }(baseClass)),
  113. _a = unobserves,
  114. _b;
  115. }
  116. var isTargetObservers = Symbol();
  117. var isEnabled = Symbol();
  118. var getObservers = Symbol();
  119. /**
  120. * Observe a target's property for changes. When a property changes, the
  121. * provided `Observer` function will be invoked with the properties current and
  122. * previous values.
  123. *
  124. * The returned cleanup function will stop listening to changes for the
  125. * provided `Observer`.
  126. *
  127. * @template T The observed target type.
  128. * @template K The observed property.
  129. * @param target - The target to observe.
  130. * @param property - The property of the target to observe.
  131. * @param observer - An observer function to invoke each time the property
  132. * changes.
  133. * @return A cleanup function that will stop observing changes for the provided
  134. * `Observer`.
  135. */
  136. export function observeProperty(target, property, observer) {
  137. var observerPrototype = installObserver(target);
  138. var observers = observerPrototype[getObservers](property);
  139. observers.push(observer);
  140. return function () {
  141. observers.splice(observers.indexOf(observer), 1);
  142. };
  143. }
  144. /**
  145. * Installs a `TargetObservers` for the provided target (if not already
  146. * installed).
  147. *
  148. * A target's `TargetObservers` is installed as a Proxy on the target's
  149. * prototype.
  150. *
  151. * @template T The observed target type.
  152. * @param target - The target to observe.
  153. * @return The installed `TargetObservers` for the provided target.
  154. */
  155. function installObserver(target) {
  156. var e_4, _a, e_5, _b;
  157. var prototype = Object.getPrototypeOf(target);
  158. if (prototype[isTargetObservers]) {
  159. return prototype;
  160. }
  161. // Proxy prototypes will not trap plain properties (not a getter/setter) that
  162. // are already defined. They only work on new plain properties.
  163. // We can work around this by deleting the properties, installing the Proxy,
  164. // then re-setting the properties.
  165. var existingKeyValues = new Map();
  166. var keys = Object.getOwnPropertyNames(target);
  167. try {
  168. for (var keys_1 = __values(keys), keys_1_1 = keys_1.next(); !keys_1_1.done; keys_1_1 = keys_1.next()) {
  169. var key = keys_1_1.value;
  170. var descriptor = getDescriptor(target, key);
  171. if (descriptor && descriptor.writable) {
  172. existingKeyValues.set(key, descriptor.value);
  173. delete target[key];
  174. }
  175. }
  176. }
  177. catch (e_4_1) { e_4 = { error: e_4_1 }; }
  178. finally {
  179. try {
  180. if (keys_1_1 && !keys_1_1.done && (_a = keys_1.return)) _a.call(keys_1);
  181. }
  182. finally { if (e_4) throw e_4.error; }
  183. }
  184. var proxy = new Proxy(Object.create(prototype), {
  185. get: function (target, key, receiver) {
  186. return Reflect.get(target, key, receiver);
  187. },
  188. set: function (target, key, newValue, receiver) {
  189. var e_6, _a;
  190. var isTargetObserversKey = key === isTargetObservers ||
  191. key === isEnabled || key === getObservers;
  192. var previous = Reflect.get(target, key, receiver);
  193. // Do not use receiver when setting the target's key. We do not want
  194. // to change whatever the target's inherent receiver is.
  195. Reflect.set(target, key, newValue);
  196. if (!isTargetObserversKey && proxy[isEnabled] &&
  197. newValue !== previous) {
  198. try {
  199. for (var _b = __values(proxy[getObservers](key)), _c = _b.next(); !_c.done; _c = _b.next()) {
  200. var observer = _c.value;
  201. observer(newValue, previous);
  202. }
  203. }
  204. catch (e_6_1) { e_6 = { error: e_6_1 }; }
  205. finally {
  206. try {
  207. if (_c && !_c.done && (_a = _b.return)) _a.call(_b);
  208. }
  209. finally { if (e_6) throw e_6.error; }
  210. }
  211. }
  212. return true;
  213. }
  214. });
  215. proxy[isTargetObservers] = true;
  216. proxy[isEnabled] = true;
  217. var observersMap = new Map();
  218. proxy[getObservers] = function (key) {
  219. var observers = observersMap.get(key) || [];
  220. if (!observersMap.has(key)) {
  221. observersMap.set(key, observers);
  222. }
  223. return observers;
  224. };
  225. Object.setPrototypeOf(target, proxy);
  226. try {
  227. // Re-set plain pre-existing properties so that the Proxy can trap them
  228. for (var _c = __values(existingKeyValues.entries()), _d = _c.next(); !_d.done; _d = _c.next()) {
  229. var _e = __read(_d.value, 2), key = _e[0], value = _e[1];
  230. target[key] = value;
  231. }
  232. }
  233. catch (e_5_1) { e_5 = { error: e_5_1 }; }
  234. finally {
  235. try {
  236. if (_d && !_d.done && (_b = _c.return)) _b.call(_c);
  237. }
  238. finally { if (e_5) throw e_5.error; }
  239. }
  240. return proxy;
  241. }
  242. /**
  243. * Enables or disables all observers for a provided target. Changes to observed
  244. * properties will not call any observers when disabled.
  245. *
  246. * @template T The observed target type.
  247. * @param target - The target to enable or disable observers for.
  248. * @param enabled - True to enable or false to disable observers.
  249. */
  250. export function setObserversEnabled(target, enabled) {
  251. var prototype = Object.getPrototypeOf(target);
  252. if (prototype[isTargetObservers]) {
  253. prototype[isEnabled] = enabled;
  254. }
  255. }
  256. //# sourceMappingURL=observer-proxy.js.map