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POHow to handle view model with multiple aggregate roots?
 

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    <p>At the moment, i got quite badly fashioned view model.</p> <p>Classes looks like this=></p> <pre><code> public class AccountActionsForm { public Reader Reader { get; set; } //something... } </code></pre> <p>Problem is that Reader type comes from domain model (violation of SRP).</p> <p>Basically, i'm looking for design tips (i.e. is it a good idea to split view model to inputs/outputs?) how to make my view model friction-less and developer friendly (i.e. - mapping should work automatically using controller base class)?</p> <p>I'm aware of AutoMapper framework and i'm likely going to use it.</p> <p>So, once more - what are common gotchas when trying to create proper view model? How to structure it? How mapping is done when there's a multiple domain object input necessary?</p> <hr> <p>I'm confused about cases when view needs data from more than 1 aggregate root. I'm creating app which has entities like Library, Reader, BibliographicRecord etc.</p> <p>In my case - at domain level, it makes no sense to group all those 3 types into <code>LibraryReaderThatHasOrderedSomeBooks</code> or whatnot, but view that should display list about ordered books for specific reader in specific library needs them all.</p> <p>So - it seems fine to create view <code>OrderedBooksList</code> with <code>OrderedBooksListModel</code> view model underneath that holds <code>LibraryOutput</code>, <code>ReaderOutput</code> and <code>BibliographicRecordOutput</code> view models. Or even better - <code>OrderedBooksListModel</code> view model, that leverages <a href="http://automapper.codeplex.com/wikipage?title=Flattening&amp;referringTitle=Home" rel="nofollow noreferrer">flattening technique</a> and has props like <code>ReaderFirstName</code>, <code>LibraryName</code> etc.</p> <p>But that leads to mapping problems because there are more than one input.<br> It's not 1:1 relation anymore where i kick in one aggregate root only.<br> Does that mean my domain model is kind a wrong?</p> <p>And what about view model fields that live purely on UI layer (i.e. enum that indicates checked tab)?</p> <p>Is <a href="https://stackoverflow.com/questions/944334/asp-net-mvc-view-with-multiple-models/944371#944371">this</a> what everyone does in such a cases?</p> <pre><code> FooBarViewData fbvd = new FooBarViewData(); fbvd.Foo = new Foo(){ A = "aaa"}; fbvd.Bar = new Bar(){ B = "bbb"}; return View(fbvd); </code></pre> <p>I'm not willing to do this=></p> <pre><code>var fbvd = new FooBarViewData(); fbvd.FooOutput = _mapper.Map&lt;Foo,FooOutput&gt;(new Foo(){ A = "aaa"}); fbvd.BarOutput = _mapper.Map&lt;Bar,BarOutput&gt;(new Bar(){ B = "bbb"}); return View(fbvd); </code></pre> <p>Seems like a lot of writing. :)</p> <hr> <p><a href="http://www.lostechies.com/blogs/jimmy_bogard/archive/2009/06/29/how-we-do-mvc-view-models.aspx" rel="nofollow noreferrer">Reading this</a> at the moment. And <a href="http://codebetter.com/blogs/jeremy.miller/archive/2008/10/23/our-opinions-on-the-asp-net-mvc-introducing-the-thunderdome-principle.aspx" rel="nofollow noreferrer">this</a>.</p> <hr> <p>Ok. I thought about this issue a lot and yeah - adding another abstraction layer seems like a solution =></p> <p><a href="http://i46.tinypic.com/fe14qp.jpg" rel="nofollow noreferrer">alt text http://i46.tinypic.com/fe14qp.jpg</a></p> <p>So - in my mind this already works, now it's time for some toying. </p> <p>ty Jimmy</p>
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