从Prism中学习设计模式之Event Aggregator 模式
从Prism中学习设计模式之Event Aggregator 模式
Event Aggregator 模式定义：渠道事件从多个对象通过一个单一的对象来简化clients的注册。
结构图：
Prism的Event Aggregator 模式：Event Aggregator允许多对象定位和发布、订阅事件。
我们从Prism源代码中德EventAggregator和CompositePresentationEvent可以学习它是如何管理和传递事件消息的。
1 public interface IEventAggregator
2 {
3 TEventType GetEvent<TEventType>() where TEventType : EventBase, new ();
4 }
5
6 public class EventAggregator : IEventAggregator
7 {
8 private readonly Dictionary<Type, EventBase> events = new Dictionary<Type, EventBase> ();
9
10 public TEventType GetEvent<TEventType>() where TEventType : EventBase, new ()
11 {
12 EventBase existingEvent = null ;
13
14 if (! this .events.TryGetValue( typeof (TEventType), out existingEvent))
15 {
16 TEventType newEvent = new TEventType();
17 this .events[ typeof (TEventType)] = newEvent;
18
19 return newEvent;
20 }
21 else
22 {
23 return (TEventType)existingEvent;
24 }
25 }
26 }
27
28 public class CompositePresentationEvent<TPayload> : EventBase
29 {
30 private IDispatcherFacade uiDispatcher;
31
32 private IDispatcherFacade UIDispatcher
33 {
34 get
35 {
36 if (uiDispatcher == null )
37 {
38 this .uiDispatcher = new DefaultDispatcher();
39 }
40
41 return uiDispatcher;
42 }
43 }
44
45 public SubscriptionToken Subscribe(Action<TPayload> action)
46 {
47 return Subscribe(action, ThreadOption.PublisherThread);
48 }
49
50 public SubscriptionToken Subscribe(Action<TPayload> action, ThreadOption threadOption)
51 {
52 return Subscribe(action, threadOption, false );
53 }
54
55 public SubscriptionToken Subscribe(Action<TPayload> action, bool keepSubscriberReferenceAlive)
56 {
57 return Subscribe(action, ThreadOption.PublisherThread, keepSubscriberReferenceAlive);
58 }
59
60 public SubscriptionToken Subscribe(Action<TPayload> action, ThreadOption threadOption, bool keepSubscriberReferenceAlive)
61 {
62 return Subscribe(action, threadOption, keepSubscriberReferenceAlive, null );
63 }
64
65 public virtual SubscriptionToken Subscribe(Action<TPayload> action, ThreadOption threadOption, bool keepSubscriberReferenceAlive, Predicate<TPayload> filter)
66 {
67 IDelegateReference actionReference = new DelegateReference(action, keepSubscriberReferenceAlive);
68 IDelegateReference filterReference;
69 if (filter != null )
70 {
71 filterReference = new DelegateReference(filter, keepSubscriberReferenceAlive);
72 }
73 else
74 {
75 filterReference = new DelegateReference( new Predicate<TPayload>( delegate { return true ; }), true );
76 }
77 EventSubscription<TPayload> subscription;
78 switch (threadOption)
79 {
80 case ThreadOption.PublisherThread:
81 subscription = new EventSubscription<TPayload> (actionReference, filterReference);
82 break ;
83 case ThreadOption.BackgroundThread:
84 subscription = new BackgroundEventSubscription<TPayload> (actionReference, filterReference);
85 break ;
86 case ThreadOption.UIThread:
87 subscription = new DispatcherEventSubscription<TPayload> (actionReference, filterReference, UIDispatcher);
88 break ;
89 default :
90 subscription = new EventSubscription<TPayload> (actionReference, filterReference);
91 break ;
92 }
93
94
95 return base .InternalSubscribe(subscription);
96 }
97
98 public virtual void Publish(TPayload payload)
99 {
100 base .InternalPublish(payload);
101 }
102
103 public virtual void Unsubscribe(Action<TPayload> subscriber)
104 {
105 lock (Subscriptions)
106 {
107 IEventSubscription eventSubscription = Subscriptions.Cast<EventSubscription<TPayload>>().FirstOrDefault(evt => evt.Action == subscriber);
108 if (eventSubscription != null )
109 {
110 Subscriptions.Remove(eventSubscription);
111 }
112 }
113 }
114
115 public virtual bool Contains(Action<TPayload> subscriber)
116 {
117 IEventSubscription eventSubscription;
118 lock (Subscriptions)
119 {
120 eventSubscription = Subscriptions.Cast<EventSubscription<TPayload>>().FirstOrDefault(evt => evt.Action == subscriber);
121 }
122 return eventSubscription != null ;
123 }
124
125 }
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比较定位
简单用法：
1 public class Model{
2 private readonly IEventAggregator eventAggregator;
3
4 this .eventAggregator = eventAggregator;
5 this .eventAggregator.GetEvent<UpdatedEvent>().Subscribe( this .Updated, ThreadOption.UIThread);
6
7 private void Updated()
8 {
9 // Todo Something
10 }
11
12 }
13
14 public class UpdatedEvent: CompositePresentationEvent<IDictionary< string , decimal >>
15 {
16 }
参考资料：
http://HdhCmsTestmartinfowler测试数据/eaaDev/EventAggregator.html
分类: .Net
标签: C# , WPF , Prism
作者： Leo_wl
出处： http://HdhCmsTestcnblogs测试数据/Leo_wl/
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