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POReducing Repositories to Aggregate Roots
 

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    <p>I currently have a repository for just about every table in the database and would like to further align myself with DDD by reducing them to aggregate roots only.</p> <p>Let’s assume that I have the following tables, <code>User</code> and <code>Phone</code>. Each user might have one or more phones. Without the notion of aggregate root I might do something like this:</p> <pre><code>//assuming I have the userId in session for example and I want to update a phone number List&lt;Phone&gt; phones = PhoneRepository.GetPhoneNumberByUserId(userId); phones[0].Number = “911”; PhoneRepository.Update(phones[0]); </code></pre> <p>The concept of aggregate roots is easier to understand on paper than in practice. I will never have phone numbers that do not belong to a User, so would it make sense to do away with the PhoneRepository and incorporate phone related methods into the UserRepository? Assuming the answer is yes, I’m going to rewrite the prior code sample.</p> <p>Am I allowed to have a method on the UserRepository that returns phone numbers? Or should it always return a reference to a User, and then traverse the relationship through the User to get to the phone numbers:</p> <pre><code>List&lt;Phone&gt; phones = UserRepository.GetPhoneNumbers(userId); // Or User user = UserRepository.GetUserWithPhoneNumbers(userId); //this method will join to Phone </code></pre> <p>Regardless of which way I acquire the phones, assuming I modified one of them, how do I go about updating them? My limited understanding is that objects under the root should be updated through the root, which would steer me towards choice #1 below. Although this will work perfectly well with Entity Framework, this seems extremely un-descriptive, because reading the code I have no idea what I’m actually updating, even though Entity Framework is keeping tab on changed objects within the graph.</p> <pre><code>UserRepository.Update(user); // Or UserRepository.UpdatePhone(phone); </code></pre> <p>Lastly, assuming I have several lookup tables that are not really tied to anything, such as <code>CountryCodes</code>, <code>ColorsCodes</code>, <code>SomethingElseCodes</code>. I might use them to populate drop downs or for whatever other reason. Are these standalone repositories? Can they be combined into some sort of logical grouping/repository such as <code>CodesRepository</code>? Or is that against best practices.</p>
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    1. COIndeed a very good question, that I've been struggling with myself a lot. Seems like one of those trade-off points where there is no "right" solution. While the answers available at the time I write this are good and covers most problems, I don't feel like they provide any "final" solutions.. :(
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    2. COI hear you, there is no limit to how close to the "right" solution one can get. I guess we have to make due with our best until we learn a better way :)
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    3. CO+1 - I am struggling with this as well. Before I had separate repo and service layer for every table. I started to combine these where it made sense, but then I ended up with a repo and service layer with over 1k lines of code. In my latest application slice, I have backed up a bit to only put closely related concepts in the same repo/service layer even if that item is dependent. eg - for a blog, I was adding comments to the post repo aggregate, but now I have separated them out to separate comment repo/service.
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