| // Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| part of dart.core; |
| |
| /// A collection of key/value pairs, from which you retrieve a value |
| /// using its associated key. |
| /// |
| /// There is a finite number of keys in the map, |
| /// and each key has exactly one value associated with it. |
| /// |
| /// Maps, and their keys and values, can be iterated. |
| /// The order of iteration is defined by the individual type of map. |
| /// Examples: |
| /// |
| /// * The plain [HashMap] is unordered (no order is guaranteed), |
| /// * the [LinkedHashMap] iterates in key insertion order, |
| /// * and a sorted map like [SplayTreeMap] iterates the keys in sorted order. |
| /// |
| /// It is generally not allowed to modify the map (add or remove keys) while |
| /// an operation is being performed on the map, for example in functions called |
| /// during a [forEach] or [putIfAbsent] call. |
| /// Modifying the map while iterating the keys or values |
| /// may also break the iteration. |
| /// |
| /// It is generally not allowed to modify the equality of keys (and thus not |
| /// their hashcode) while they are in the map. Some specialized subtypes may be |
| /// more permissive, in which case they should document this behavior. |
| abstract class Map<K, V> { |
| /// Creates an empty [LinkedHashMap]. |
| /// |
| /// This constructor is equivalent to the non-const map literal `<K,V>{}`. |
| /// |
| /// A `LinkedHashMap` requires the keys to implement compatible |
| /// `operator==` and `hashCode`. |
| /// It iterates in key insertion order. |
| external factory Map(); |
| |
| /// Creates a [LinkedHashMap] with the same keys and values as [other]. |
| /// |
| /// The keys must all be instances of [K] and the values of [V]. |
| /// The [other] map itself can have any type, unlike for [Map.of], |
| /// and the key and value types are checked (and can fail) at run-time. |
| /// |
| /// Prefer using [Map.of] when possible, and only use `Map.from` |
| /// to create a new map with more precise types than the original, |
| /// and when it's known that all the keys and values have those |
| /// more precise types. |
| /// |
| /// A `LinkedHashMap` requires the keys to implement compatible |
| /// `operator==` and `hashCode`. |
| /// It iterates in key insertion order. |
| factory Map.from(Map other) = LinkedHashMap<K, V>.from; |
| |
| /// Creates a [LinkedHashMap] with the same keys and values as [other]. |
| /// |
| /// A `LinkedHashMap` requires the keys to implement compatible |
| /// `operator==` and `hashCode`, and it allows `null` as a key. |
| /// It iterates in key insertion order. |
| factory Map.of(Map<K, V> other) = LinkedHashMap<K, V>.of; |
| |
| /// Creates an unmodifiable hash-based map containing the entries of [other]. |
| /// |
| /// The keys must all be instances of [K] and the values of [V]. |
| /// The [other] map itself can have any type. |
| /// |
| /// The map requires the keys to implement compatible |
| /// `operator==` and `hashCode`. |
| /// The created map iterates keys in a fixed order, |
| /// preserving the order provided by [other]. |
| /// |
| /// The resulting map behaves like the result of [Map.from], |
| /// except that the map returned by this constructor is not modifiable. |
| external factory Map.unmodifiable(Map<dynamic, dynamic> other); |
| |
| /// Creates an identity map with the default implementation, [LinkedHashMap]. |
| /// |
| /// An identity map uses [identical] for equality and [identityHashCode] |
| /// for hash codes of keys instead of the intrinsic [Object.==] and |
| /// [Object.hashCode] of the keys. |
| /// |
| /// The map iterates in key insertion order. |
| factory Map.identity() = LinkedHashMap<K, V>.identity; |
| |
| /// Creates a Map instance in which the keys and values are computed from the |
| /// [iterable]. |
| /// |
| /// For each element of the [iterable], a key/value pair is computed |
| /// by applying [key] and [value] respectively to the element of the iterable. |
| /// |
| /// Equivalent to the map literal: |
| /// ```dart |
| /// <K, V>{for (var v in iterable) key(v): value(v)} |
| /// ``` |
| /// The literal is generally preferable because it allows |
| /// for a more precise typing. |
| /// |
| /// The example below creates a new map from a list of integers. |
| /// The keys of `map` are the `list` values converted to strings, |
| /// and the values of the `map` are the squares of the `list` values: |
| /// ```dart |
| /// List<int> list = [1, 2, 3]; |
| /// var map = Map<String, int>.fromIterable(list, |
| /// key: (item) => item.toString(), |
| /// value: (item) => item * item); |
| /// // map is {"1": 1, "2": 4, "3": 9} |
| /// ``` |
| /// If no values are specified for [key] and [value], |
| /// the default is the identity function. |
| /// In that case, the iterable element must be assignable to the |
| /// key or value type of the created map. |
| /// |
| /// In the following example, the keys and corresponding values of `map` |
| /// are the `list` values directly: |
| /// ```dart |
| /// var map = Map<int, int>.fromIterable(list); |
| /// // map is {1: 1, 2: 2, 3: 3} |
| /// ``` |
| /// The keys computed by the source [iterable] do not need to be unique. |
| /// The last occurrence of a key will overwrite |
| /// the value of any previous occurrence. |
| /// |
| /// The created map is a [LinkedHashMap]. |
| /// A `LinkedHashMap` requires the keys to implement compatible |
| /// `operator==` and `hashCode`. |
| /// It iterates in key insertion order. |
| factory Map.fromIterable(Iterable iterable, |
| {K key(dynamic element)?, |
| V value(dynamic element)?}) = LinkedHashMap<K, V>.fromIterable; |
| |
| /// Creates a map associating the given [keys] to the given [values]. |
| /// |
| /// The map construction iterates over [keys] and [values] simultaneously, |
| /// and adds an entry to the map for each pair of key and value. |
| /// ```dart |
| /// List<String> letters = ['b', 'c']; |
| /// List<String> words = ['bad', 'cat']; |
| /// var map = Map.fromIterables(letters, words); |
| /// // map is {"b": "bad", "c": "cat"} |
| /// ``` |
| /// If [keys] contains the same object multiple times, |
| /// the value of the last occurrence overwrites any previous value. |
| /// |
| /// The two [Iterable]s must have the same length. |
| /// |
| /// The created map is a [LinkedHashMap]. |
| /// A `LinkedHashMap` requires the keys to implement compatible |
| /// `operator==` and `hashCode`. |
| /// It iterates in key insertion order. |
| factory Map.fromIterables(Iterable<K> keys, Iterable<V> values) = |
| LinkedHashMap<K, V>.fromIterables; |
| |
| /// Adapts [source] to be a `Map<K2, V2>`. |
| /// |
| /// Any time the set would produce a key or value that is not a [K2] or [V2], |
| /// the access will throw. |
| /// |
| /// Any time [K2] key or [V2] value is attempted added into the adapted map, |
| /// the store will throw unless the key is also an instance of [K] and |
| /// the value is also an instance of [V]. |
| /// |
| /// If all accessed entries of [source] are have [K2] keys and [V2] values |
| /// and if all entries added to the returned map have [K] keys and [V]] values, |
| /// then the returned map can be used as a `Map<K2, V2>`. |
| static Map<K2, V2> castFrom<K, V, K2, V2>(Map<K, V> source) => |
| CastMap<K, V, K2, V2>(source); |
| |
| /// Creates a new map and adds all entries. |
| /// |
| /// Returns a new `Map<K, V>` where all entries of [entries] |
| /// have been added in iteration order. |
| /// |
| /// If multiple [entries] have the same key, |
| /// later occurrences overwrite the value of the earlier ones. |
| /// |
| /// Equivalent to the map literal: |
| /// ```dart |
| /// <K, V>{for (var e in entries) e.key: e.value} |
| /// ``` |
| factory Map.fromEntries(Iterable<MapEntry<K, V>> entries) => |
| <K, V>{}..addEntries(entries); |
| |
| /// Provides a view of this map as having [RK] keys and [RV] instances, |
| /// if necessary. |
| /// |
| /// If this map is already a `Map<RK, RV>`, it is returned unchanged. |
| /// |
| /// If this set contains only keys of type [RK] and values of type [RV], |
| /// all read operations will work correctly. |
| /// If any operation exposes a non-[RK] key or non-[RV] value, |
| /// the operation will throw instead. |
| /// |
| /// Entries added to the map must be valid for both a `Map<K, V>` and a |
| /// `Map<RK, RV>`. |
| Map<RK, RV> cast<RK, RV>(); |
| |
| /// Whether this map contains the given [value]. |
| /// |
| /// Returns true if any of the values in the map are equal to `value` |
| /// according to the `==` operator. |
| bool containsValue(Object? value); |
| |
| /// Whether this map contains the given [key]. |
| /// |
| /// Returns true if any of the keys in the map are equal to `key` |
| /// according to the equality used by the map. |
| bool containsKey(Object? key); |
| |
| /// The value for the given [key], or `null` if [key] is not in the map. |
| /// |
| /// Some maps allow `null` as a value. |
| /// For those maps, a lookup using this operator cannot distinguish between a |
| /// key not being in the map, and the key being there with a `null` value. |
| /// Methods like [containsKey] or [putIfAbsent] can be used if the distinction |
| /// is important. |
| V? operator [](Object? key); |
| |
| /// Associates the [key] with the given [value]. |
| /// |
| /// If the key was already in the map, its associated value is changed. |
| /// Otherwise the key/value pair is added to the map. |
| void operator []=(K key, V value); |
| |
| /// The map entries of [this]. |
| Iterable<MapEntry<K, V>> get entries; |
| |
| /// Returns a new map where all entries of this map are transformed by |
| /// the given [convert] function. |
| Map<K2, V2> map<K2, V2>(MapEntry<K2, V2> convert(K key, V value)); |
| |
| /// Adds all key/value pairs of [newEntries] to this map. |
| /// |
| /// If a key of [newEntries] is already in this map, |
| /// the corresponding value is overwritten. |
| /// |
| /// The operation is equivalent to doing `this[entry.key] = entry.value` |
| /// for each [MapEntry] of the iterable. |
| void addEntries(Iterable<MapEntry<K, V>> newEntries); |
| |
| /// Updates the value for the provided [key]. |
| /// |
| /// Returns the new value associated with the key. |
| /// |
| /// If the key is present, invokes [update] with the current value and stores |
| /// the new value in the map. |
| /// |
| /// If the key is not present and [ifAbsent] is provided, calls [ifAbsent] |
| /// and adds the key with the returned value to the map. |
| /// |
| /// If the key is not present, [ifAbsent] must be provided. |
| V update(K key, V update(V value), {V ifAbsent()?}); |
| |
| /// Updates all values. |
| /// |
| /// Iterates over all entries in the map and updates them with the result |
| /// of invoking [update]. |
| void updateAll(V update(K key, V value)); |
| |
| /// Removes all entries of this map that satisfy the given [test]. |
| void removeWhere(bool test(K key, V value)); |
| |
| /// Look up the value of [key], or add a new entry if it isn't there. |
| /// |
| /// Returns the value associated to [key], if there is one. |
| /// Otherwise calls [ifAbsent] to get a new value, associates [key] to |
| /// that value, and then returns the new value. |
| /// ```dart |
| /// Map<String, int> scores = {'Bob': 36}; |
| /// for (var key in ['Bob', 'Rohan', 'Sophena']) { |
| /// scores.putIfAbsent(key, () => key.length); |
| /// } |
| /// scores['Bob']; // 36 |
| /// scores['Rohan']; // 5 |
| /// scores['Sophena']; // 7 |
| /// ``` |
| /// Calling [ifAbsent] must not add or remove keys from the map. |
| V putIfAbsent(K key, V ifAbsent()); |
| |
| /// Adds all key/value pairs of [other] to this map. |
| /// |
| /// If a key of [other] is already in this map, its value is overwritten. |
| /// |
| /// The operation is equivalent to doing `this[key] = value` for each key |
| /// and associated value in other. It iterates over [other], which must |
| /// therefore not change during the iteration. |
| void addAll(Map<K, V> other); |
| |
| /// Removes [key] and its associated value, if present, from the map. |
| /// |
| /// Returns the value associated with `key` before it was removed. |
| /// Returns `null` if `key` was not in the map. |
| /// |
| /// Note that some maps allow `null` as a value, |
| /// so a returned `null` value doesn't always mean that the key was absent. |
| V? remove(Object? key); |
| |
| /// Removes all entries from the map. |
| /// |
| /// After this, the map is empty. |
| void clear(); |
| |
| /// Applies [action] to each key/value pair of the map. |
| /// |
| /// Calling `action` must not add or remove keys from the map. |
| void forEach(void action(K key, V value)); |
| |
| /// The keys of [this]. |
| /// |
| /// The returned iterable has efficient `length` and `contains` operations, |
| /// based on [length] and [containsKey] of the map. |
| /// |
| /// The order of iteration is defined by the individual `Map` implementation, |
| /// but must be consistent between changes to the map. |
| /// |
| /// Modifying the map while iterating the keys may break the iteration. |
| Iterable<K> get keys; |
| |
| /// The values of [this]. |
| /// |
| /// The values are iterated in the order of their corresponding keys. |
| /// This means that iterating [keys] and [values] in parallel will |
| /// provide matching pairs of keys and values. |
| /// |
| /// The returned iterable has an efficient `length` method based on the |
| /// [length] of the map. Its [Iterable.contains] method is based on |
| /// `==` comparison. |
| /// |
| /// Modifying the map while iterating the values may break the iteration. |
| Iterable<V> get values; |
| |
| /// The number of key/value pairs in the map. |
| int get length; |
| |
| /// Whether there is no key/value pair in the map. |
| bool get isEmpty; |
| |
| /// Whether there is at least one key/value pair in the map. |
| bool get isNotEmpty; |
| } |
| |
| /// A key/value pair representing an entry in a [Map]. |
| class MapEntry<K, V> { |
| /// The key of the entry. |
| final K key; |
| |
| /// The value associated to [key] in the map. |
| final V value; |
| |
| /// Creates an entry with [key] and [value]. |
| const factory MapEntry(K key, V value) = MapEntry<K, V>._; |
| |
| const MapEntry._(this.key, this.value); |
| |
| String toString() => "MapEntry($key: $value)"; |
| } |