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| 1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file | |
| 2 // for details. All rights reserved. Use of this source code is governed by a | |
| 3 // BSD-style license that can be found in the LICENSE file. | |
| 4 | |
| 5 library observe.src.path_observer; | |
| 6 | |
| 7 import 'dart:async'; | |
| 8 import 'dart:collection'; | |
| 9 import 'dart:math' show min; | |
| 10 | |
| 11 import 'package:logging/logging.dart' show Logger, Level; | |
| 12 import 'package:observe/observe.dart'; | |
| 13 import 'package:smoke/smoke.dart' as smoke; | |
| 14 | |
| 15 import 'package:utf/utf.dart' show stringToCodepoints; | |
| 16 | |
| 17 /// A data-bound path starting from a view-model or model object, for example | |
| 18 /// `foo.bar.baz`. | |
| 19 /// | |
| 20 /// When [open] is called, this will observe changes to the object and any | |
| 21 /// intermediate object along the path, and send updated values accordingly. | |
| 22 /// When [close] is called it will stop observing the objects. | |
| 23 /// | |
| 24 /// This class is used to implement `Node.bind` and similar functionality in | |
| 25 /// the [template_binding](pub.dartlang.org/packages/template_binding) package. | |
| 26 class PathObserver extends _Observer implements Bindable { | |
| 27 PropertyPath _path; | |
| 28 Object _object; | |
| 29 _ObservedSet _directObserver; | |
| 30 | |
| 31 /// Observes [path] on [object] for changes. This returns an object | |
| 32 /// that can be used to get the changes and get/set the value at this path. | |
| 33 /// | |
| 34 /// The path can be a [PropertyPath], or a [String] used to construct it. | |
| 35 /// | |
| 36 /// See [open] and [value]. | |
| 37 PathObserver(Object object, [path]) | |
| 38 : _object = object, | |
| 39 _path = new PropertyPath(path); | |
| 40 | |
| 41 PropertyPath get path => _path; | |
| 42 | |
| 43 /// Sets the value at this path. | |
| 44 void set value(newValue) { | |
| 45 if (_path != null) _path.setValueFrom(_object, newValue); | |
| 46 } | |
| 47 | |
| 48 int get _reportArgumentCount => 2; | |
| 49 | |
| 50 /// Initiates observation and returns the initial value. | |
| 51 /// The callback will be passed the updated [value], and may optionally be | |
| 52 /// declared to take a second argument, which will contain the previous value. | |
| 53 open(callback) => super.open(callback); | |
| 54 | |
| 55 void _connect() { | |
| 56 _directObserver = new _ObservedSet(this, _object); | |
| 57 _check(skipChanges: true); | |
| 58 } | |
| 59 | |
| 60 void _disconnect() { | |
| 61 _value = null; | |
| 62 if (_directObserver != null) { | |
| 63 _directObserver.close(this); | |
| 64 _directObserver = null; | |
| 65 } | |
| 66 // Dart note: the JS impl does not do this, but it seems consistent with | |
| 67 // CompoundObserver. After closing the PathObserver can't be reopened. | |
| 68 _path = null; | |
| 69 _object = null; | |
| 70 } | |
| 71 | |
| 72 void _iterateObjects(void observe(obj, prop)) { | |
| 73 _path._iterateObjects(_object, observe); | |
| 74 } | |
| 75 | |
| 76 bool _check({bool skipChanges: false}) { | |
| 77 var oldValue = _value; | |
| 78 _value = _path.getValueFrom(_object); | |
| 79 if (skipChanges || _value == oldValue) return false; | |
| 80 | |
| 81 _report(_value, oldValue, this); | |
| 82 return true; | |
| 83 } | |
| 84 } | |
| 85 | |
| 86 /// A dot-delimieted property path such as "foo.bar" or "foo.10.bar". | |
| 87 /// | |
| 88 /// The path specifies how to get a particular value from an object graph, where | |
| 89 /// the graph can include arrays and maps. Each segment of the path describes | |
| 90 /// how to take a single step in the object graph. Properties like 'foo' or | |
| 91 /// 'bar' are read as properties on objects, or as keys if the object is a [Map] | |
| 92 /// or a [Indexable], while integer values are read as indexes in a [List]. | |
| 93 // TODO(jmesserly): consider specialized subclasses for: | |
| 94 // * empty path | |
| 95 // * "value" | |
| 96 // * single token in path, e.g. "foo" | |
| 97 class PropertyPath { | |
| 98 /// The segments of the path. | |
| 99 final List<Object> _segments; | |
| 100 | |
| 101 /// Creates a new [PropertyPath]. These can be stored to avoid excessive | |
| 102 /// parsing of path strings. | |
| 103 /// | |
| 104 /// The provided [path] should be a String or a List. If it is a list it | |
| 105 /// should contain only Symbols and integers. This can be used to avoid | |
| 106 /// parsing. | |
| 107 /// | |
| 108 /// Note that this constructor will canonicalize identical paths in some cases | |
| 109 /// to save memory, but this is not guaranteed. Use [==] for comparions | |
| 110 /// purposes instead of [identical]. | |
| 111 // Dart note: this is ported from `function getPath`. | |
| 112 factory PropertyPath([path]) { | |
| 113 if (path is PropertyPath) return path; | |
| 114 if (path == null || (path is List && path.isEmpty)) path = ''; | |
| 115 | |
| 116 if (path is List) { | |
| 117 var copy = new List.from(path, growable: false); | |
| 118 for (var segment in copy) { | |
| 119 // Dart note: unlike Javascript, we don't support arbitraty objects that | |
| 120 // can be converted to a String. | |
| 121 // TODO(sigmund): consider whether we should support that here. It might | |
| 122 // be easier to add support for that if we switch first to use strings | |
| 123 // for everything instead of symbols. | |
| 124 if (segment is! int && segment is! String && segment is! Symbol) { | |
| 125 throw new ArgumentError( | |
| 126 'List must contain only ints, Strings, and Symbols'); | |
| 127 } | |
| 128 } | |
| 129 return new PropertyPath._(copy); | |
| 130 } | |
| 131 | |
| 132 var pathObj = _pathCache[path]; | |
| 133 if (pathObj != null) return pathObj; | |
| 134 | |
| 135 | |
| 136 final segments = new _PathParser().parse(path); | |
| 137 if (segments == null) return _InvalidPropertyPath._instance; | |
| 138 | |
| 139 // TODO(jmesserly): we could use an UnmodifiableListView here, but that adds | |
| 140 // memory overhead. | |
| 141 pathObj = new PropertyPath._(segments.toList(growable: false)); | |
| 142 if (_pathCache.length >= _pathCacheLimit) { | |
| 143 _pathCache.remove(_pathCache.keys.first); | |
| 144 } | |
| 145 _pathCache[path] = pathObj; | |
| 146 return pathObj; | |
| 147 } | |
| 148 | |
| 149 PropertyPath._(this._segments); | |
| 150 | |
| 151 int get length => _segments.length; | |
| 152 bool get isEmpty => _segments.isEmpty; | |
| 153 bool get isValid => true; | |
| 154 | |
| 155 String toString() { | |
| 156 if (!isValid) return '<invalid path>'; | |
| 157 var sb = new StringBuffer(); | |
| 158 bool first = true; | |
| 159 for (var key in _segments) { | |
| 160 if (key is Symbol) { | |
| 161 if (!first) sb.write('.'); | |
| 162 sb.write(smoke.symbolToName(key)); | |
| 163 } else { | |
| 164 _formatAccessor(sb, key); | |
| 165 } | |
| 166 first = false; | |
| 167 } | |
| 168 return sb.toString(); | |
| 169 } | |
| 170 | |
| 171 _formatAccessor(StringBuffer sb, Object key) { | |
| 172 if (key is int) { | |
| 173 sb.write('[$key]'); | |
| 174 } else { | |
| 175 sb.write('["${key.toString().replaceAll('"', '\\"')}"]'); | |
| 176 } | |
| 177 } | |
| 178 | |
| 179 bool operator ==(other) { | |
| 180 if (identical(this, other)) return true; | |
| 181 if (other is! PropertyPath) return false; | |
| 182 if (isValid != other.isValid) return false; | |
| 183 | |
| 184 int len = _segments.length; | |
| 185 if (len != other._segments.length) return false; | |
| 186 for (int i = 0; i < len; i++) { | |
| 187 if (_segments[i] != other._segments[i]) return false; | |
| 188 } | |
| 189 return true; | |
| 190 } | |
| 191 | |
| 192 /// This is the [Jenkins hash function][1] but using masking to keep | |
| 193 /// values in SMI range. | |
| 194 /// [1]: http://en.wikipedia.org/wiki/Jenkins_hash_function | |
| 195 // TODO(jmesserly): should reuse this instead, see | |
| 196 // https://code.google.com/p/dart/issues/detail?id=11617 | |
| 197 int get hashCode { | |
| 198 int hash = 0; | |
| 199 for (int i = 0, len = _segments.length; i < len; i++) { | |
| 200 hash = 0x1fffffff & (hash + _segments[i].hashCode); | |
| 201 hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10)); | |
| 202 hash = hash ^ (hash >> 6); | |
| 203 } | |
| 204 hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3)); | |
| 205 hash = hash ^ (hash >> 11); | |
| 206 return 0x1fffffff & (hash + ((0x00003fff & hash) << 15)); | |
| 207 } | |
| 208 | |
| 209 /// Returns the current value of the path from the provided [obj]ect. | |
| 210 getValueFrom(Object obj) { | |
| 211 if (!isValid) return null; | |
| 212 for (var segment in _segments) { | |
| 213 if (obj == null) return null; | |
| 214 obj = _getObjectProperty(obj, segment); | |
| 215 } | |
| 216 return obj; | |
| 217 } | |
| 218 | |
| 219 /// Attempts to set the [value] of the path from the provided [obj]ect. | |
| 220 /// Returns true if and only if the path was reachable and set. | |
| 221 bool setValueFrom(Object obj, Object value) { | |
| 222 var end = _segments.length - 1; | |
| 223 if (end < 0) return false; | |
| 224 for (int i = 0; i < end; i++) { | |
| 225 if (obj == null) return false; | |
| 226 obj = _getObjectProperty(obj, _segments[i]); | |
| 227 } | |
| 228 return _setObjectProperty(obj, _segments[end], value); | |
| 229 } | |
| 230 | |
| 231 void _iterateObjects(Object obj, void observe(obj, prop)) { | |
| 232 if (!isValid || isEmpty) return; | |
| 233 | |
| 234 int i = 0, last = _segments.length - 1; | |
| 235 while (obj != null) { | |
| 236 // _segments[i] is passed to indicate that we are only observing that | |
| 237 // property of obj. See observe declaration in _ObservedSet. | |
| 238 observe(obj, _segments[i]); | |
| 239 | |
| 240 if (i >= last) break; | |
| 241 obj = _getObjectProperty(obj, _segments[i++]); | |
| 242 } | |
| 243 } | |
| 244 | |
| 245 // Dart note: it doesn't make sense to have compiledGetValueFromFn in Dart. | |
| 246 } | |
| 247 | |
| 248 | |
| 249 /// Visible only for testing: | |
| 250 getSegmentsOfPropertyPathForTesting(p) => p._segments; | |
| 251 | |
| 252 class _InvalidPropertyPath extends PropertyPath { | |
| 253 static final _instance = new _InvalidPropertyPath(); | |
| 254 | |
| 255 bool get isValid => false; | |
| 256 _InvalidPropertyPath() : super._([]); | |
| 257 } | |
| 258 | |
| 259 bool _changeRecordMatches(record, key) { | |
| 260 if (record is PropertyChangeRecord) { | |
| 261 return (record as PropertyChangeRecord).name == key; | |
| 262 } | |
| 263 if (record is MapChangeRecord) { | |
| 264 if (key is Symbol) key = smoke.symbolToName(key); | |
| 265 return (record as MapChangeRecord).key == key; | |
| 266 } | |
| 267 return false; | |
| 268 } | |
| 269 | |
| 270 /// Properties in [Map] that need to be read as properties and not as keys in | |
| 271 /// the map. We exclude methods ('containsValue', 'containsKey', 'putIfAbsent', | |
| 272 /// 'addAll', 'remove', 'clear', 'forEach') because there is no use in reading | |
| 273 /// them as part of path-observer segments. | |
| 274 const _MAP_PROPERTIES = const [#keys, #values, #length, #isEmpty, #isNotEmpty]; | |
| 275 | |
| 276 _getObjectProperty(object, property) { | |
| 277 if (object == null) return null; | |
| 278 | |
| 279 if (property is int) { | |
| 280 if (object is List && property >= 0 && property < object.length) { | |
| 281 return object[property]; | |
| 282 } | |
| 283 } else if (property is String) { | |
| 284 return object[property]; | |
| 285 } else if (property is Symbol) { | |
| 286 // Support indexer if available, e.g. Maps or polymer_expressions Scope. | |
| 287 // This is the default syntax used by polymer/nodebind and | |
| 288 // polymer/observe-js PathObserver. | |
| 289 // TODO(sigmund): should we also support using checking dynamically for | |
| 290 // whether the type practically implements the indexer API | |
| 291 // (smoke.hasInstanceMethod(type, const Symbol('[]')))? | |
| 292 if (object is Indexable || object is Map && !_MAP_PROPERTIES.contains(proper
ty)) { | |
| 293 return object[smoke.symbolToName(property)]; | |
| 294 } | |
| 295 try { | |
| 296 return smoke.read(object, property); | |
| 297 } on NoSuchMethodError catch (e) { | |
| 298 // Rethrow, unless the type implements noSuchMethod, in which case we | |
| 299 // interpret the exception as a signal that the method was not found. | |
| 300 // Dart note: getting invalid properties is an error, unlike in JS where | |
| 301 // it returns undefined. | |
| 302 if (!smoke.hasNoSuchMethod(object.runtimeType)) rethrow; | |
| 303 } | |
| 304 } | |
| 305 | |
| 306 if (_logger.isLoggable(Level.FINER)) { | |
| 307 _logger.finer("can't get $property in $object"); | |
| 308 } | |
| 309 return null; | |
| 310 } | |
| 311 | |
| 312 bool _setObjectProperty(object, property, value) { | |
| 313 if (object == null) return false; | |
| 314 | |
| 315 if (property is int) { | |
| 316 if (object is List && property >= 0 && property < object.length) { | |
| 317 object[property] = value; | |
| 318 return true; | |
| 319 } | |
| 320 } else if (property is Symbol) { | |
| 321 // Support indexer if available, e.g. Maps or polymer_expressions Scope. | |
| 322 if (object is Indexable || object is Map && !_MAP_PROPERTIES.contains(proper
ty)) { | |
| 323 object[smoke.symbolToName(property)] = value; | |
| 324 return true; | |
| 325 } | |
| 326 try { | |
| 327 smoke.write(object, property, value); | |
| 328 return true; | |
| 329 } on NoSuchMethodError catch (e, s) { | |
| 330 if (!smoke.hasNoSuchMethod(object.runtimeType)) rethrow; | |
| 331 } | |
| 332 } | |
| 333 | |
| 334 if (_logger.isLoggable(Level.FINER)) { | |
| 335 _logger.finer("can't set $property in $object"); | |
| 336 } | |
| 337 return false; | |
| 338 } | |
| 339 | |
| 340 // From: https://github.com/rafaelw/ChangeSummary/blob/master/change_summary.js | |
| 341 | |
| 342 final _identRegExp = () { | |
| 343 const identStart = '[\$_a-zA-Z]'; | |
| 344 const identPart = '[\$_a-zA-Z0-9]'; | |
| 345 return new RegExp('^$identStart+$identPart*\$'); | |
| 346 }(); | |
| 347 | |
| 348 _isIdent(s) => _identRegExp.hasMatch(s); | |
| 349 | |
| 350 // Dart note: refactored to convert to codepoints once and operate on codepoints | |
| 351 // rather than characters. | |
| 352 class _PathParser { | |
| 353 List keys = []; | |
| 354 int index = -1; | |
| 355 String key; | |
| 356 | |
| 357 final Map<String, List<String>> _pathStateMachine = { | |
| 358 'beforePath': { | |
| 359 'ws': ['beforePath'], | |
| 360 'ident': ['inIdent', 'append'], | |
| 361 '[': ['beforeElement'], | |
| 362 'eof': ['afterPath'] | |
| 363 }, | |
| 364 | |
| 365 'inPath': { | |
| 366 'ws': ['inPath'], | |
| 367 '.': ['beforeIdent'], | |
| 368 '[': ['beforeElement'], | |
| 369 'eof': ['afterPath'] | |
| 370 }, | |
| 371 | |
| 372 'beforeIdent': { | |
| 373 'ws': ['beforeIdent'], | |
| 374 'ident': ['inIdent', 'append'] | |
| 375 }, | |
| 376 | |
| 377 'inIdent': { | |
| 378 'ident': ['inIdent', 'append'], | |
| 379 '0': ['inIdent', 'append'], | |
| 380 'number': ['inIdent', 'append'], | |
| 381 'ws': ['inPath', 'push'], | |
| 382 '.': ['beforeIdent', 'push'], | |
| 383 '[': ['beforeElement', 'push'], | |
| 384 'eof': ['afterPath', 'push'] | |
| 385 }, | |
| 386 | |
| 387 'beforeElement': { | |
| 388 'ws': ['beforeElement'], | |
| 389 '0': ['afterZero', 'append'], | |
| 390 'number': ['inIndex', 'append'], | |
| 391 "'": ['inSingleQuote', 'append', ''], | |
| 392 '"': ['inDoubleQuote', 'append', ''] | |
| 393 }, | |
| 394 | |
| 395 'afterZero': { | |
| 396 'ws': ['afterElement', 'push'], | |
| 397 ']': ['inPath', 'push'] | |
| 398 }, | |
| 399 | |
| 400 'inIndex': { | |
| 401 '0': ['inIndex', 'append'], | |
| 402 'number': ['inIndex', 'append'], | |
| 403 'ws': ['afterElement'], | |
| 404 ']': ['inPath', 'push'] | |
| 405 }, | |
| 406 | |
| 407 'inSingleQuote': { | |
| 408 "'": ['afterElement'], | |
| 409 'eof': ['error'], | |
| 410 'else': ['inSingleQuote', 'append'] | |
| 411 }, | |
| 412 | |
| 413 'inDoubleQuote': { | |
| 414 '"': ['afterElement'], | |
| 415 'eof': ['error'], | |
| 416 'else': ['inDoubleQuote', 'append'] | |
| 417 }, | |
| 418 | |
| 419 'afterElement': { | |
| 420 'ws': ['afterElement'], | |
| 421 ']': ['inPath', 'push'] | |
| 422 } | |
| 423 }; | |
| 424 | |
| 425 /// From getPathCharType: determines the type of a given [code]point. | |
| 426 String _getPathCharType(code) { | |
| 427 if (code == null) return 'eof'; | |
| 428 switch(code) { | |
| 429 case 0x5B: // [ | |
| 430 case 0x5D: // ] | |
| 431 case 0x2E: // . | |
| 432 case 0x22: // " | |
| 433 case 0x27: // ' | |
| 434 case 0x30: // 0 | |
| 435 return _char(code); | |
| 436 | |
| 437 case 0x5F: // _ | |
| 438 case 0x24: // $ | |
| 439 return 'ident'; | |
| 440 | |
| 441 case 0x20: // Space | |
| 442 case 0x09: // Tab | |
| 443 case 0x0A: // Newline | |
| 444 case 0x0D: // Return | |
| 445 case 0xA0: // No-break space | |
| 446 case 0xFEFF: // Byte Order Mark | |
| 447 case 0x2028: // Line Separator | |
| 448 case 0x2029: // Paragraph Separator | |
| 449 return 'ws'; | |
| 450 } | |
| 451 | |
| 452 // a-z, A-Z | |
| 453 if ((0x61 <= code && code <= 0x7A) || (0x41 <= code && code <= 0x5A)) | |
| 454 return 'ident'; | |
| 455 | |
| 456 // 1-9 | |
| 457 if (0x31 <= code && code <= 0x39) | |
| 458 return 'number'; | |
| 459 | |
| 460 return 'else'; | |
| 461 } | |
| 462 | |
| 463 static String _char(int codepoint) => new String.fromCharCodes([codepoint]); | |
| 464 | |
| 465 void push() { | |
| 466 if (key == null) return; | |
| 467 | |
| 468 // Dart note: we store the keys with different types, rather than | |
| 469 // parsing/converting things later in toString. | |
| 470 if (_isIdent(key)) { | |
| 471 keys.add(smoke.nameToSymbol(key)); | |
| 472 } else { | |
| 473 var index = int.parse(key, radix: 10, onError: (_) => null); | |
| 474 keys.add(index != null ? index : key); | |
| 475 } | |
| 476 key = null; | |
| 477 } | |
| 478 | |
| 479 void append(newChar) { | |
| 480 key = (key == null) ? newChar : '$key$newChar'; | |
| 481 } | |
| 482 | |
| 483 bool _maybeUnescapeQuote(String mode, codePoints) { | |
| 484 if (index >= codePoints.length) return false; | |
| 485 var nextChar = _char(codePoints[index + 1]); | |
| 486 if ((mode == 'inSingleQuote' && nextChar == "'") || | |
| 487 (mode == 'inDoubleQuote' && nextChar == '"')) { | |
| 488 index++; | |
| 489 append(nextChar); | |
| 490 return true; | |
| 491 } | |
| 492 return false; | |
| 493 } | |
| 494 | |
| 495 /// Returns the parsed keys, or null if there was a parse error. | |
| 496 List<String> parse(String path) { | |
| 497 var codePoints = stringToCodepoints(path); | |
| 498 var mode = 'beforePath'; | |
| 499 | |
| 500 while (mode != null) { | |
| 501 index++; | |
| 502 var c = index >= codePoints.length ? null : codePoints[index]; | |
| 503 | |
| 504 if (c != null && | |
| 505 _char(c) == '\\' && _maybeUnescapeQuote(mode, codePoints)) continue; | |
| 506 | |
| 507 var type = _getPathCharType(c); | |
| 508 if (mode == 'error') return null; | |
| 509 | |
| 510 var typeMap = _pathStateMachine[mode]; | |
| 511 var transition = typeMap[type]; | |
| 512 if (transition == null) transition = typeMap['else']; | |
| 513 if (transition == null) return null; // parse error; | |
| 514 | |
| 515 mode = transition[0]; | |
| 516 var actionName = transition.length > 1 ? transition[1] : null; | |
| 517 if (actionName == 'push' && key != null) push(); | |
| 518 if (actionName == 'append') { | |
| 519 var newChar = transition.length > 2 && transition[2] != null | |
| 520 ? transition[2] : _char(c); | |
| 521 append(newChar); | |
| 522 } | |
| 523 | |
| 524 if (mode == 'afterPath') return keys; | |
| 525 } | |
| 526 return null; // parse error | |
| 527 } | |
| 528 } | |
| 529 | |
| 530 final Logger _logger = new Logger('observe.PathObserver'); | |
| 531 | |
| 532 | |
| 533 /// This is a simple cache. It's like LRU but we don't update an item on a | |
| 534 /// cache hit, because that would require allocation. Better to let it expire | |
| 535 /// and reallocate the PropertyPath. | |
| 536 // TODO(jmesserly): this optimization is from observe-js, how valuable is it in | |
| 537 // practice? | |
| 538 final _pathCache = new LinkedHashMap<String, PropertyPath>(); | |
| 539 | |
| 540 /// The size of a path like "foo.bar" is approximately 160 bytes, so this | |
| 541 /// reserves ~16Kb of memory for recently used paths. Since paths are frequently | |
| 542 /// reused, the theory is that this ends up being a good tradeoff in practice. | |
| 543 // (Note: the 160 byte estimate is from Dart VM 1.0.0.10_r30798 on x64 without | |
| 544 // using UnmodifiableListView in PropertyPath) | |
| 545 const int _pathCacheLimit = 100; | |
| 546 | |
| 547 /// [CompoundObserver] is a [Bindable] object which knows how to listen to | |
| 548 /// multiple values (registered via [addPath] or [addObserver]) and invoke a | |
| 549 /// callback when one or more of the values have changed. | |
| 550 /// | |
| 551 /// var obj = new ObservableMap.from({'a': 1, 'b': 2}); | |
| 552 /// var otherObj = new ObservableMap.from({'c': 3}); | |
| 553 /// | |
| 554 /// var observer = new CompoundObserver() | |
| 555 /// ..addPath(obj, 'a'); | |
| 556 /// ..addObserver(new PathObserver(obj, 'b')); | |
| 557 /// ..addPath(otherObj, 'c'); | |
| 558 /// ..open((values) { | |
| 559 /// for (int i = 0; i < values.length; i++) { | |
| 560 /// print('The value at index $i is now ${values[i]}'); | |
| 561 /// } | |
| 562 /// }); | |
| 563 /// | |
| 564 /// obj['a'] = 10; // print will be triggered async | |
| 565 /// | |
| 566 class CompoundObserver extends _Observer implements Bindable { | |
| 567 _ObservedSet _directObserver; | |
| 568 bool _reportChangesOnOpen; | |
| 569 List _observed = []; | |
| 570 | |
| 571 CompoundObserver([this._reportChangesOnOpen = false]) { | |
| 572 _value = []; | |
| 573 } | |
| 574 | |
| 575 int get _reportArgumentCount => 3; | |
| 576 | |
| 577 /// Initiates observation and returns the initial value. | |
| 578 /// The callback will be passed the updated [value], and may optionally be | |
| 579 /// declared to take a second argument, which will contain the previous value. | |
| 580 /// | |
| 581 /// Implementation note: a third argument can also be declared, which will | |
| 582 /// receive a list of objects and paths, such that `list[2 * i]` will access | |
| 583 /// the object and `list[2 * i + 1]` will access the path, where `i` is the | |
| 584 /// order of the [addPath] call. This parameter is only used by | |
| 585 /// `package:polymer` as a performance optimization, and should not be relied | |
| 586 /// on in new code. | |
| 587 open(callback) => super.open(callback); | |
| 588 | |
| 589 void _connect() { | |
| 590 for (var i = 0; i < _observed.length; i += 2) { | |
| 591 var object = _observed[i]; | |
| 592 if (!identical(object, _observerSentinel)) { | |
| 593 _directObserver = new _ObservedSet(this, object); | |
| 594 break; | |
| 595 } | |
| 596 } | |
| 597 | |
| 598 _check(skipChanges: !_reportChangesOnOpen); | |
| 599 } | |
| 600 | |
| 601 void _disconnect() { | |
| 602 for (var i = 0; i < _observed.length; i += 2) { | |
| 603 if (identical(_observed[i], _observerSentinel)) { | |
| 604 _observed[i + 1].close(); | |
| 605 } | |
| 606 } | |
| 607 | |
| 608 _observed = null; | |
| 609 _value = null; | |
| 610 | |
| 611 if (_directObserver != null) { | |
| 612 _directObserver.close(this); | |
| 613 _directObserver = null; | |
| 614 } | |
| 615 } | |
| 616 | |
| 617 /// Adds a dependency on the property [path] accessed from [object]. | |
| 618 /// [path] can be a [PropertyPath] or a [String]. If it is omitted an empty | |
| 619 /// path will be used. | |
| 620 void addPath(Object object, [path]) { | |
| 621 if (_isOpen || _isClosed) { | |
| 622 throw new StateError('Cannot add paths once started.'); | |
| 623 } | |
| 624 | |
| 625 path = new PropertyPath(path); | |
| 626 _observed..add(object)..add(path); | |
| 627 if (!_reportChangesOnOpen) return; | |
| 628 _value.add(path.getValueFrom(object)); | |
| 629 } | |
| 630 | |
| 631 void addObserver(Bindable observer) { | |
| 632 if (_isOpen || _isClosed) { | |
| 633 throw new StateError('Cannot add observers once started.'); | |
| 634 } | |
| 635 | |
| 636 _observed..add(_observerSentinel)..add(observer); | |
| 637 if (!_reportChangesOnOpen) return; | |
| 638 _value.add(observer.open((_) => deliver())); | |
| 639 } | |
| 640 | |
| 641 void _iterateObjects(void observe(obj, prop)) { | |
| 642 for (var i = 0; i < _observed.length; i += 2) { | |
| 643 var object = _observed[i]; | |
| 644 if (!identical(object, _observerSentinel)) { | |
| 645 (_observed[i + 1] as PropertyPath)._iterateObjects(object, observe); | |
| 646 } | |
| 647 } | |
| 648 } | |
| 649 | |
| 650 bool _check({bool skipChanges: false}) { | |
| 651 bool changed = false; | |
| 652 _value.length = _observed.length ~/ 2; | |
| 653 var oldValues = null; | |
| 654 for (var i = 0; i < _observed.length; i += 2) { | |
| 655 var object = _observed[i]; | |
| 656 var path = _observed[i + 1]; | |
| 657 var value; | |
| 658 if (identical(object, _observerSentinel)) { | |
| 659 var observable = path as Bindable; | |
| 660 value = _state == _Observer._UNOPENED ? | |
| 661 observable.open((_) => this.deliver()) : | |
| 662 observable.value; | |
| 663 } else { | |
| 664 value = (path as PropertyPath).getValueFrom(object); | |
| 665 } | |
| 666 | |
| 667 if (skipChanges) { | |
| 668 _value[i ~/ 2] = value; | |
| 669 continue; | |
| 670 } | |
| 671 | |
| 672 if (value == _value[i ~/ 2]) continue; | |
| 673 | |
| 674 // don't allocate this unless necessary. | |
| 675 if (_notifyArgumentCount >= 2) { | |
| 676 if (oldValues == null) oldValues = new Map(); | |
| 677 oldValues[i ~/ 2] = _value[i ~/ 2]; | |
| 678 } | |
| 679 | |
| 680 changed = true; | |
| 681 _value[i ~/ 2] = value; | |
| 682 } | |
| 683 | |
| 684 if (!changed) return false; | |
| 685 | |
| 686 // TODO(rafaelw): Having _observed as the third callback arg here is | |
| 687 // pretty lame API. Fix. | |
| 688 _report(_value, oldValues, _observed); | |
| 689 return true; | |
| 690 } | |
| 691 } | |
| 692 | |
| 693 /// An object accepted by [PropertyPath] where properties are read and written | |
| 694 /// as indexing operations, just like a [Map]. | |
| 695 abstract class Indexable<K, V> { | |
| 696 V operator [](K key); | |
| 697 operator []=(K key, V value); | |
| 698 } | |
| 699 | |
| 700 const _observerSentinel = const _ObserverSentinel(); | |
| 701 class _ObserverSentinel { const _ObserverSentinel(); } | |
| 702 | |
| 703 // Visible for testing | |
| 704 get observerSentinelForTesting => _observerSentinel; | |
| 705 | |
| 706 // A base class for the shared API implemented by PathObserver and | |
| 707 // CompoundObserver and used in _ObservedSet. | |
| 708 abstract class _Observer extends Bindable { | |
| 709 Function _notifyCallback; | |
| 710 int _notifyArgumentCount; | |
| 711 var _value; | |
| 712 | |
| 713 // abstract members | |
| 714 void _iterateObjects(void observe(obj, prop)); | |
| 715 void _connect(); | |
| 716 void _disconnect(); | |
| 717 bool _check({bool skipChanges: false}); | |
| 718 | |
| 719 static int _UNOPENED = 0; | |
| 720 static int _OPENED = 1; | |
| 721 static int _CLOSED = 2; | |
| 722 int _state = _UNOPENED; | |
| 723 bool get _isOpen => _state == _OPENED; | |
| 724 bool get _isClosed => _state == _CLOSED; | |
| 725 | |
| 726 /// The number of arguments the subclass will pass to [_report]. | |
| 727 int get _reportArgumentCount; | |
| 728 | |
| 729 open(callback) { | |
| 730 if (_isOpen || _isClosed) { | |
| 731 throw new StateError('Observer has already been opened.'); | |
| 732 } | |
| 733 | |
| 734 if (smoke.minArgs(callback) > _reportArgumentCount) { | |
| 735 throw new ArgumentError('callback should take $_reportArgumentCount or ' | |
| 736 'fewer arguments'); | |
| 737 } | |
| 738 | |
| 739 _notifyCallback = callback; | |
| 740 _notifyArgumentCount = min(_reportArgumentCount, smoke.maxArgs(callback)); | |
| 741 | |
| 742 _connect(); | |
| 743 _state = _OPENED; | |
| 744 return _value; | |
| 745 } | |
| 746 | |
| 747 get value => _discardChanges(); | |
| 748 | |
| 749 void close() { | |
| 750 if (!_isOpen) return; | |
| 751 | |
| 752 _disconnect(); | |
| 753 _value = null; | |
| 754 _notifyCallback = null; | |
| 755 _state = _CLOSED; | |
| 756 } | |
| 757 | |
| 758 _discardChanges() { | |
| 759 _check(skipChanges: true); | |
| 760 return _value; | |
| 761 } | |
| 762 | |
| 763 void deliver() { | |
| 764 if (_isOpen) _dirtyCheck(); | |
| 765 } | |
| 766 | |
| 767 bool _dirtyCheck() { | |
| 768 var cycles = 0; | |
| 769 while (cycles < _MAX_DIRTY_CHECK_CYCLES && _check()) { | |
| 770 cycles++; | |
| 771 } | |
| 772 return cycles > 0; | |
| 773 } | |
| 774 | |
| 775 void _report(newValue, oldValue, [extraArg]) { | |
| 776 try { | |
| 777 switch (_notifyArgumentCount) { | |
| 778 case 0: _notifyCallback(); break; | |
| 779 case 1: _notifyCallback(newValue); break; | |
| 780 case 2: _notifyCallback(newValue, oldValue); break; | |
| 781 case 3: _notifyCallback(newValue, oldValue, extraArg); break; | |
| 782 } | |
| 783 } catch (e, s) { | |
| 784 // Deliver errors async, so if a single callback fails it doesn't prevent | |
| 785 // other things from working. | |
| 786 new Completer().completeError(e, s); | |
| 787 } | |
| 788 } | |
| 789 } | |
| 790 | |
| 791 /// The observedSet abstraction is a perf optimization which reduces the total | |
| 792 /// number of Object.observe observations of a set of objects. The idea is that | |
| 793 /// groups of Observers will have some object dependencies in common and this | |
| 794 /// observed set ensures that each object in the transitive closure of | |
| 795 /// dependencies is only observed once. The observedSet acts as a write barrier | |
| 796 /// such that whenever any change comes through, all Observers are checked for | |
| 797 /// changed values. | |
| 798 /// | |
| 799 /// Note that this optimization is explicitly moving work from setup-time to | |
| 800 /// change-time. | |
| 801 /// | |
| 802 /// TODO(rafaelw): Implement "garbage collection". In order to move work off | |
| 803 /// the critical path, when Observers are closed, their observed objects are | |
| 804 /// not Object.unobserve(d). As a result, it's possible that if the observedSet | |
| 805 /// is kept open, but some Observers have been closed, it could cause "leaks" | |
| 806 /// (prevent otherwise collectable objects from being collected). At some | |
| 807 /// point, we should implement incremental "gc" which keeps a list of | |
| 808 /// observedSets which may need clean-up and does small amounts of cleanup on a | |
| 809 /// timeout until all is clean. | |
| 810 class _ObservedSet { | |
| 811 /// To prevent sequential [PathObserver]s and [CompoundObserver]s from | |
| 812 /// observing the same object, we check if they are observing the same root | |
| 813 /// as the most recently created observer, and if so merge it into the | |
| 814 /// existing _ObservedSet. | |
| 815 /// | |
| 816 /// See <https://github.com/Polymer/observe-js/commit/f0990b1> and | |
| 817 /// <https://codereview.appspot.com/46780044/>. | |
| 818 static _ObservedSet _lastSet; | |
| 819 | |
| 820 /// The root object for a [PathObserver]. For a [CompoundObserver], the root | |
| 821 /// object of the first path observed. This is used by the constructor to | |
| 822 /// reuse an [_ObservedSet] that starts from the same object. | |
| 823 Object _rootObject; | |
| 824 | |
| 825 /// Subset of properties in [_rootObject] that we care about. | |
| 826 Set _rootObjectProperties; | |
| 827 | |
| 828 /// Observers associated with this root object, in birth order. | |
| 829 final List<_Observer> _observers = []; | |
| 830 | |
| 831 // Dart note: the JS implementation is O(N^2) because Array.indexOf is used | |
| 832 // for lookup in this array. We use HashMap to avoid this problem. It | |
| 833 // also gives us a nice way of tracking the StreamSubscription. | |
| 834 Map<Object, StreamSubscription> _objects; | |
| 835 | |
| 836 factory _ObservedSet(_Observer observer, Object rootObject) { | |
| 837 if (_lastSet == null || !identical(_lastSet._rootObject, rootObject)) { | |
| 838 _lastSet = new _ObservedSet._(rootObject); | |
| 839 } | |
| 840 _lastSet.open(observer, rootObject); | |
| 841 return _lastSet; | |
| 842 } | |
| 843 | |
| 844 _ObservedSet._(rootObject) | |
| 845 : _rootObject = rootObject, | |
| 846 _rootObjectProperties = rootObject == null ? null : new Set(); | |
| 847 | |
| 848 void open(_Observer obs, Object rootObject) { | |
| 849 if (_rootObject == null) { | |
| 850 _rootObject = rootObject; | |
| 851 _rootObjectProperties = new Set(); | |
| 852 } | |
| 853 | |
| 854 _observers.add(obs); | |
| 855 obs._iterateObjects(observe); | |
| 856 } | |
| 857 | |
| 858 void close(_Observer obs) { | |
| 859 _observers.remove(obs); | |
| 860 if (_observers.isNotEmpty) return; | |
| 861 | |
| 862 if (_objects != null) { | |
| 863 for (var sub in _objects.values) sub.cancel(); | |
| 864 _objects = null; | |
| 865 } | |
| 866 _rootObject = null; | |
| 867 _rootObjectProperties = null; | |
| 868 if (identical(_lastSet, this)) _lastSet = null; | |
| 869 } | |
| 870 | |
| 871 /// Observe now takes a second argument to indicate which property of an | |
| 872 /// object is being observed, so we don't trigger change notifications on | |
| 873 /// changes to unrelated properties. | |
| 874 void observe(Object obj, Object prop) { | |
| 875 if (identical(obj, _rootObject)) _rootObjectProperties.add(prop); | |
| 876 if (obj is ObservableList) _observeStream(obj.listChanges); | |
| 877 if (obj is Observable) _observeStream(obj.changes); | |
| 878 } | |
| 879 | |
| 880 void _observeStream(Stream stream) { | |
| 881 // TODO(jmesserly): we hash on streams as we have two separate change | |
| 882 // streams for ObservableList. Not sure if that is the design we will use | |
| 883 // going forward. | |
| 884 | |
| 885 if (_objects == null) _objects = new HashMap(); | |
| 886 if (!_objects.containsKey(stream)) { | |
| 887 _objects[stream] = stream.listen(_callback); | |
| 888 } | |
| 889 } | |
| 890 | |
| 891 /// Whether we can ignore all change events in [records]. This is true if all | |
| 892 /// records are for properties in the [_rootObject] and we are not observing | |
| 893 /// any of those properties. Changes on objects other than [_rootObject], or | |
| 894 /// changes for properties in [_rootObjectProperties] can't be ignored. | |
| 895 // Dart note: renamed from `allRootObjNonObservedProps` in the JS code. | |
| 896 bool _canIgnoreRecords(List<ChangeRecord> records) { | |
| 897 for (var rec in records) { | |
| 898 if (rec is PropertyChangeRecord) { | |
| 899 if (!identical(rec.object, _rootObject) || | |
| 900 _rootObjectProperties.contains(rec.name)) { | |
| 901 return false; | |
| 902 } | |
| 903 } else if (rec is ListChangeRecord) { | |
| 904 if (!identical(rec.object, _rootObject) || | |
| 905 _rootObjectProperties.contains(rec.index)) { | |
| 906 return false; | |
| 907 } | |
| 908 } else { | |
| 909 // TODO(sigmund): consider adding object to MapChangeRecord, and make | |
| 910 // this more precise. | |
| 911 return false; | |
| 912 } | |
| 913 } | |
| 914 return true; | |
| 915 } | |
| 916 | |
| 917 void _callback(records) { | |
| 918 if (_canIgnoreRecords(records)) return; | |
| 919 for (var observer in _observers.toList(growable: false)) { | |
| 920 if (observer._isOpen) observer._iterateObjects(observe); | |
| 921 } | |
| 922 | |
| 923 for (var observer in _observers.toList(growable: false)) { | |
| 924 if (observer._isOpen) observer._check(); | |
| 925 } | |
| 926 } | |
| 927 } | |
| 928 | |
| 929 const int _MAX_DIRTY_CHECK_CYCLES = 1000; | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2989763002:
Update charted to 0.4.8 and roll (Closed)
