| // 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, `null`, `dart:ffi` pointers, |
| /// `dart:ffi` structs, or `dart:ffi` unions. |
| /// |
| /// 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"; |
| |
| /// 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, `null`, a |
| /// `dart:ffi` pointer, a `dart:ffi` struct, or a `dart:ffi` union. |
| 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, `null`, a |
| /// `dart:ffi` pointer, a `dart:ffi` struct, or a `dart:ffi` union. |
| external void operator []=(Object object, T? value); |
| } |