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POWhere to put needed initialization code when using Dependency Injection?
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copied!<p>When my constructors are pure arguments-to-propeties setters then I'm not sure where to put other code that a class needs to properly work.</p> <p>For example in JavaScript I'm programming a <code>WindowMessageController</code> that processes <code>message</code> events on the <code>window</code> object.</p> <p>In order for this to work, I must somewhere attach the handler:</p> <pre><code>var controller = this; this.applicableWindow.addEventListener("message", function(event) { controller.messageAction(event.data); } </code></pre> <p><strong>Where does this stuff correctly belongs?</strong></p> <ol> <li>in the constructor</li> <li>in the .initialize() method - introduces temporal coupling</li> <li>in the WindowMessageControllerFactory.create(applicableWindow) - quite a distant place for so central piece of code. This means that even such a small class would be split into two pieces.</li> <li>in the composition root itself - this would multiply its size when doing all the time</li> <li>in some other class WindowMessageRouter that would have only one method, the constructor, with this code</li> </ol> <p><strong>EDIT</strong></p> <p>This case seems special because there is usually only one instance of such a controller in an app. However in more generalized case what would be the answer if I was creating an instances of <code>Button</code> class that would wrap over some DOM <code><button /></code> element? Suddeny a </p> <pre><code>button = buttonFactory.create(domButtonEl); </code></pre> <p>seems much more useful.</p>

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