hunt.proton.engine.ExtendableAccessor source code

1 /*
2  * hunt-proton: AMQP Protocol library for D programming language.
3  *
4  * Copyright (C) 2018-2019 HuntLabs
5  *
6  * Website: https://www.huntlabs.net/
7  *
8  * Licensed under the Apache-2.0 License.
9  *
10  */
11 
12 module hunt.proton.engine.ExtendableAccessor;
13 
14 import hunt.proton.engine.Extendable;
15 import hunt.proton.engine.Record;
16 import hunt.Exceptions;
17 
18 /**
19  * A typesafe convenience class for associating additional data with {@link Extendable} classes.
20  * <p>
21  * An instance of <code>ExtendableAccessor</code> uses itself as the key in the {@link Extendable#attachments()}
22  * so it's best instantiated as a static member.
23  * <pre><code>
24  *   class Foo extends BaseHandler {
25  *     private static ExtendableAccessor&lt;Link, Bar&gt; LINK_BAR = new ExtendableAccessor&lt;&gt;(Bar.class);
26  *     void onLinkRemoteOpen(Event e) {
27  *       Bar bar = LINK_BAR.get(e.getLink());
28  *       if (bar is null) {
29  *         bar = new Bar();
30  *         LINK_BAR.set(e.getLink(), bar);
31  *         }
32  *       }
33  *     }
34  * </code></pre>
35  * 
36  * @param <E> An {@link Extendable} type where the data is to be stored
37  * @param <T> The type of the data to be stored
38  */
39 class ExtendableAccessor(E,T) : Extendable {
40     private  TypeInfo klass;
41     this() {
42         this.klass = typeid(T);
43     }
44 
45     public T get(E e, string key) {
46         return cast(T)(e.attachments().get(key));
47     }
48 
49     public void set(E e, T value ,string key) {
50         e.attachments().set(key, cast(Object)value);
51     }
52 
53     Record attachments() {
54         implementationMissing(false);
55         return null;
56     }
57 }