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POWhich part of model should handle database inserts?
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  1. POWhich part of model should handle database inserts?
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    copied!<p>Title probably doesn't describe my problem too well, I'll be glad if somebody could edit it to something more appropriate. Anyways:</p> <p>I got a component that is supposed to return product price given its <code>id</code>. It implements an interface like this one:</p> <pre><code>interface IProductPriceFetcher { double GetPrice(int id); } </code></pre> <p>Now, the price can be fetched from <strong>3 different</strong> sources:</p> <ul> <li>web service</li> <li>directly from website source code (scrapping)</li> <li>as a final fallback (both webservice and website are inaccessible), most recent price from local database is returned</li> </ul> <p>To play around this 3-different-sources issue I've implemented class like this:</p> <pre><code>class MainFetcher : IProductPriceFetcher { public double GetPrice(int id) { var priceFetcher = this.factory.GetWebServiceFetcher() ?? this.factory.GetWebsiteFetcher() ?? this.factory.GetLocalDatabaseFetcher(); return priceFetcher.GetPrice(id); } } </code></pre> <p>Each method from factory returns <code>IProductPriceFetcher</code> of course, with side note that first two can fail and return <code>null</code>; I assumed <code>GetLocalDatabaseFetcher</code> will always return meaningful object tho.</p> <h3>My "general wondering... ment"</h3> <p>Upon successful webservice/website call, I want fetched price to be inserted into local datbase, as a future fallback case. Now my question is: which part of code above should be responsible for that? Should it be one of the concrete web fetchers that returns price? Or "aggregator" fetcher (<code>MainFetcher</code>), as it also has knowledge over what's the source of price? Should I raise some event? Inject yet another interface with DB calls? Change design to better?</p> <p>Why did it even occur as an issue to me? Well, I tried to keep the code clean (worry not, it's only pet project for my spare time - exactly for solving problems like this) possibly with SRP/SoC in mind. Now I seem to have problems switching from this mindset - I mean, how could possibly something that fetches webpages also be doing database inserts? Oh, come on! :)</p>
 

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