ember-legacy-class-transform
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# Ember WeakMap
This addon is a polyfill for the [Ember.WeakMap RFC](https://github.com/emberjs/rfcs/blob/master/text/0091-weakmap.md).
A WeakMap provides a mechanism for storing and retrieving private state. The WeakMap
itself does not retain a reference to the state, allowing the state to be reclaimed
when the key is reclaimed.
A traditional WeakMap (and the one that will be part of the ES2015 language) allows for
weakness from key -> map, and also from map -> key. This allows either the Map,
or the key being reclaimed to also release the state.
Unfortunately, this bi-directional weakness is problematic to polyfill.
Luckily, uni-directional weakness, in either direction, "just works". A polyfill
must just choose a direction.
Note: Just like ES2015 WeakMap, only non null Objects can be used as keys
## Installation
```shell
ember install ember-weakmap
```
## Usage
```js
import WeakMap from 'ember-weakmap';
var myWeakMap = new WeakMap();
```
### Set
```js
/*
* @method set
* @param key {Object}
* @param value {Any}
* @return {Any} stored value
*/
```
```js
var emailObj = { id: 1, subject: 'Hello World' };
myWeakMap.set(emailObj, {read: true});
```
The key **must be an object**.
### Get
```js
/*
* @method get
* @param key {Object}
* @return {*} stored value
*/
```
```js
myWeakMap.get(emailObj); // => { read: true }
myWeakMap.get(someObjThatWasNotSet); // => undefined
```
### Has
```js
/*
* @method has
* @param key {Object}
* @return {Boolean} if the key exists
*/
```
```js
myWeakMap.has(emailObj); // => true
myWeakMap.has(someObjThatWasNotSet); // => false
```
### Delete
```js
/*
* @method delete
* @param key {Object}
*/
```
```js
myWeakMap.delete(emailObj);
myWeakMap.get(emailObj); // => undefined
myWeakMap.has(emailObj); // false
```