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POSeemingly redundant event and event handlers
 

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    <p>I will explain with an example. My GWT project has a Company module, which lets a user add, edit, delete, select and list companies.</p> <p>Of these, the add, edit and delete operations lands back the user on the CompanyList page. Thus, having three different events - <code>CompanyAddedEvent, CompanyUpdatedEvent and CompanyDeletedEvent</code>, and their respective event handlers - seems overkill to me, as there is absolutely not difference in their function.</p> <p>Is it OK to let a single event manage the three operations? One alternative I think is to use some event like <code>CompanyListInvokedEvent</code>. However, somewhere I think its not appropriate, is the event actually is not the list being invoked, but a company being added/updated/deleted.</p> <p>If it had been only a single module, I would have get the task done with three separate events. But other 10 such modules are facing this dilemma. It means 10x3 = 30 event classes along with their 30 respective handlers. The number is large enough for me to reconsider. What would be a good solution to this?</p> <p><strong>UPDATE -</strong></p> <p>@ColinAlworth's answer made me realize that I could easily use Generics instead of my stupid solution. The following code represents an event EntityUpdatedEvent, which would be raised whenever an entity is updated.</p> <p>Event handler class -</p> <pre><code>public class EntityUpdatedEvent&lt;T&gt; extends GwtEvent&lt;EntityUpdatedEventHandler&lt;T&gt;&gt;{ private Type&lt;EntityUpdatedEventHandler&lt;T&gt;&gt; type; private final String statusMessage; public EntityUpdatedEvent(Type&lt;EntityUpdatedEventHandler&lt;T&gt;&gt; type, String statusMessage) { this.statusMessage = statusMessage; this.type = type; } public String getStatusMessage() { return this.statusMessage; } @Override public com.google.gwt.event.shared.GwtEvent.Type&lt;EntityUpdatedEventHandler&lt;T&gt;&gt; getAssociatedType() { return this.type; } @Override protected void dispatch(EntityUpdatedEventHandler&lt;T&gt; handler) { handler.onEventRaised(this); } } </code></pre> <p>Event handler interface -</p> <pre><code>public interface EntityUpdatedEventHandler&lt;T&gt; extends EventHandler { void onEventRaised(EntityUpdatedEvent&lt;T&gt; event); } </code></pre> <p>Adding the handler to event bus - </p> <pre><code>eventBus.addHandler(CompanyEventHandlerTypes.CompanyUpdated, new EntityUpdatedEventHandler&lt;Company&gt;() { @Override public void onEventRaised(EntityUpdatedEvent&lt;Company&gt; event) { History.newItem(CompanyToken.CompanyList.name()); Presenter presenter = new CompanyListPresenter(serviceBundle, eventBus, new CompanyListView(), event.getStatusMessage()); presenter.go(container); } }); </code></pre> <p>Likewise, I have two other Added and Deleted generic events, thus eliminating entire redundancy from my event-related codebase.</p> <p>Are there any suggestions on this solution?</p> <p>P.S. > <a href="http://www.mail-archive.com/google-web-toolkit-contributors@googlegroups.com/msg11692.html" rel="nofollow">This discussion</a> provides more insight on this problem.</p>
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