<p>I just watched this <a href="https://www.youtube.com/watch?v=HQtLRqqB-Kk" rel="nofollow">talk</a> by
Andrew Gerrand about Cuddle. There's a bit at around
<a href="https://youtu.be/HQtLRqqB-Kk?t=14m14s" rel="nofollow">14:14</a> where he lost me. The slides in
question are <a href="http://cuddle.googlecode.com/hg/talk/index.html#slide-11" rel="nofollow">here</a>
and <a href="http://cuddle.googlecode.com/hg/talk/index.html#slide-12" rel="nofollow">here</a>.</p>
<p>Is there something inherent to closures that make the operation safe and not
racey?</p>
<hr/>**评论：**<br/><br/>TheMerovius: <pre><p>No, it's just an API thing. Instead of giving you a transaction-type, with Rollback and Commit, the API just takes a func(appengine.Context) error, and basically does</p>
<pre><code>func RunInTransaction(c appengine.Context, fn func(appengine.Context) error) {
tx := db.Begin()
if err := fn(c); err != nil {
tx.Rollback()
} else {
tx.Commit()
}
}
</code></pre></pre>alexwhoizzle: <pre><p>Correct. Its not that the closure itself adds transactional support. Its the call to datastore.RunInTransaction that does. You need the closure to pass in your needed datastore.Get call which you want done inside of a transaction.</p></pre>
