Interfacing non local types in golang

<p>Hi,</p> <p>i have a question for all you golang ninjas! :)</p> <p>In my api code i am using the MongoDB driver mgo. I initialize the mgo.Session and mgo.Database in the InitSession method in model/db.go.</p> <p>I wrote a Datastore interface to distribute the database connection to all model methods that need db access. Now i have the following problem. My model methods cannot extend the type (db *mgo.Database) since it is no local type. Aliasing the mgo.Database type wouldn&#39;t help either since i need also access to the mgo.Database methods. I came up with an solution which feels dirty to me by wrapping the mgo.Database struct inside my own Database struct.</p> <p>Is there a more elegant solution for this problem?</p> <p>Here is the code fragment: <a href="https://gist.github.com/gdenn/24f787b2cbf5d51879ffb14036cd5e02" rel="nofollow">https://gist.github.com/gdenn/24f787b2cbf5d51879ffb14036cd5e02</a></p> <hr/>**评论：**<br/><br/>radovskyb: <pre><p>What you are doing is fine from what I can see in that snippet.</p> <p>It&#39;s actually a good practice to wrap your database types in your own types that implement interfaces as it makes it quite easy to swap out for different implementations if needed.</p> <p>I&#39;m not sure what other types of &#34;extending&#34; you need to do with your mongo database, but for that, it looks good.</p> <p>Here is an example of something similar I wrote a while back (needs some work, was out of boredom):</p> <ul> <li>Repo Interface: <a href="https://github.com/radovskyb/services/blob/master/user/datastore/repo.go" rel="nofollow">https://github.com/radovskyb/services/blob/master/user/datastore/repo.go</a></li> <li>MySQL implementation: <a href="https://github.com/radovskyb/services/blob/master/user/datastore/mysql.go" rel="nofollow">https://github.com/radovskyb/services/blob/master/user/datastore/mysql.go</a></li> <li>In memory implementation: <a href="https://github.com/radovskyb/services/blob/master/user/datastore/mock.go" rel="nofollow">https://github.com/radovskyb/services/blob/master/user/datastore/mock.go</a></li> </ul> <p>Edit: I do however suggest separating concerns a little bit better. Rather than having a single <code>Datastore</code> interface in a single <code>models</code> package, it might be better to create a separate <code>UserStore</code> which has it&#39;s own interface.</p> <p>Otherwise your <code>models</code> package might get quite cluttered in a big application.</p></pre>rap3: <pre><p>thanks radovskyb, i see your point for the interface seperation. </p></pre>dchapes: <pre><blockquote> <p>own types that inherit from interfaces</p> </blockquote> <p>It&#39;s not helpful to misuse the word &#34;inherit&#34; here. Go does not have inheritance; it does have composition via embedding.</p></pre>radovskyb: <pre><p>This is true and I should have said <code>implements interfaces</code>, but we are all human and make mistakes :P</p> <p>I edited it anyway because you are right even if we are being slightly pedantic about the point here lol!</p></pre>