-
Notifications
You must be signed in to change notification settings - Fork 1.6k
/
expando.dart
62 lines (56 loc) · 2.16 KB
/
expando.dart
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
// Copyright (c) 2012, 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;
/**
* An [Expando] allows adding new properties to objects.
*
* Does not work on numbers, strings, booleans or `null`.
*
* An `Expando` does not hold on to the added property value after an object
* becomes inaccessible.
*
* Since you can always create a new number that is identical to an existing
* number, it means that an expando property on a number could never be
* released. To avoid this, expando properties cannot be added to numbers.
* The same argument applies to strings, booleans and `null`, which also have
* literals that evaluate to identical values when they occur more than once.
*
* There is no restriction on other classes, even for compile time constant
* objects. Be careful if adding expando properties to compile time constants,
* since they will stay alive forever.
*/
class Expando<T extends Object> {
/**
* The name of the this [Expando] as passed to the constructor. If
* no name was passed to the constructor, the name is `null`.
*/
final String? name;
/**
* Creates a new [Expando]. The optional name is only used for
* debugging purposes and creating two different [Expando]s with the
* same name yields two [Expando]s that work on different properties
* of the objects they are used on.
*/
external Expando([String? name]);
/**
* Expando toString method override.
*/
String toString() => "Expando:${name.toString()}";
/**
* Gets the value of this [Expando]'s property on the given
* object. If the object hasn't been expanded, the method returns
* `null`.
*
* The object must not be a number, a string, a boolean or null.
*/
external T? operator [](Object object);
/**
* Sets the value of this [Expando]'s property on the given
* object. Properties can effectively be removed again by setting
* their value to null.
*
* The object must not be a number, a string, a boolean or null.
*/
external void operator []=(Object object, T? value);
}