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    <p>I'm not sure what do you mean by VO. Is it value object?</p> <p>I'm a huge fan of the <a href="http://en.wikipedia.org/wiki/Domain-driven_design" rel="nofollow">DDD</a> (domain driven design) approach (though I don't consider my self as guru in it). In DDD you have so called <strong><em>Services</em></strong>. <strong><em>Service</em></strong> Is an action that operates on your domain and returns data. Service encapsulates the manipulation with you Domain data.</p> <p>Instead of having the controller to do all the domain logic like what items to retrieve, what DAO's to use and etc (why controller should care about the Domain anyway?), it should be encapsulated inside the Domain it self, in DDD case inside a Service.</p> <p>So for example you want to retrieve all the Category items of the category "electronics". You could write a controller that looks like this (forgive me if the code have invalid syntax, its for the sake of example):</p> <pre><code>public function showItemsByCategoryAction($categoryName) { $categoryId = $categoryDAO-&gt;findByName($categoryName); if(is_null($categoryId)) { //@TODO error } $itemIds = $categoryLinkDAO-&gt;getItemsByCategoryId($categoryId); if(empty($itemIds)) { //@TODO show error to the user } $items = $categoryItemDAO-&gt;findManyItems($itemIds); //@TODO parse, assign to view etc } </code></pre> <p>This introduces at least two problems:</p> <ol> <li>The controller is <a href="http://survivethedeepend.com/zendframeworkbook/en/1.0/the.model#zfbook.the.model.the.fat.stupid.ugly.controller" rel="nofollow">FSUC</a> (Fat stupid ugly controller)</li> <li>The code is not reusable. If you would like to add another presentation layer (like API for developers, mobile version of the website or etc), you would have to copy-paste the same code (expect the part of the view rendering), and eventually you will come to something that will encapsulate this code, and this is what Services are for.</li> </ol> <p>With the Services layer the same controller could look like</p> <pre><code>public function showItemsByCategoryAction($categoryName) { $service = new Item_CategoryName_Finder_Service(); $items = $service-&gt;find($categoryName); if(empty($items)){ //@TODO show empty page result, redirect or whatever } $this-&gt;getView()-&gt;bind('items', $items); } </code></pre> <p>The controller is now clean, small, and all the Domain logic is encapsulated inside a service that can be reused anywhere in the code.</p> <p>Now some people believe that the controller should know nothing about DAOs and communicate with the Domain only by using Services, other says that its ok to make calls to DAOs from the controller, there are no strict rules, decide what suits better for you.</p> <p>I hope this helps you! Good luck :)</p>
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    1. USDmitry Kudryavtsev
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    1. COThe domain services I think encompases domain actions which don't fit naturally within a domain object. I don't think the domain services should return data at all, they might but this is not their purpose. This is the repository's responsability to deal with db access
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    2. CO@MikeSW Yes you probably right. But the question wasn't really about DDD, I just brought a design pattern (service) from DDD into the context of the question. If you want to go proper DDD then repository should not know anything about the database and should use DAO's to access the storage. I also heard somewhere that its better not to expose the repository, DOA and etc to the controller but instead expose only the Service layer, so controller uses different services to create/edit/manipulate/find the data within the Domain, and the services in turn uses repositories, factories and etc.
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      1. USDmitry Kudryavtsev
    3. COI kinda disagree here a bit. Only the repository should know about the db in any form. About the services, I think those are Application Services but in this case, they would be just a suplementary layer, I mean I don't think they add any value here, so the controller performs also the role of an application service.
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