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POIn Meteor, how to update one db field when another field changes?
 

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    <p>General question: in Meteor, what's the best way to implement business logic that triggers whenever a model is updated -- e.g., for updating dependent fields or validations or...</p> <p>Specific example: I'd like to add a "slug" field to Lists collection in the <a href="http://www.meteor.com/examples/todos" rel="noreferrer">Meteor todos example</a>. The slug needs to automatically update whenever a list's name is changed.</p> <p>Here's what I've got... I'm observing <em>every</em> change to a list to see if its slug needs to be created/updated. This is in a <em>shared</em> models.js (runs server and client-side, to get the benefits of latency compensation):</p> <pre class="lang-js prettyprint-override"><code>// Lists -- {name: String} Lists = new Meteor.Collection("lists"); var listsObserver = Lists.find().observe({ added: updateSlug, changed: updateSlug }); function updateSlug(doc, idx) { var slug = (doc.name || '').replace(/\W+/g, '-').toLowerCase(); if (slug !== doc.slug) { console.log("Updating slug for '" + doc.name + "' to " + slug); Lists.update(doc._id, {$set: {slug: slug}}); } } </code></pre> <p>(And as in the original todos example, server/publish.js publishes all of <code>Lists.find()</code> as "lists", and client/todos.js subscribes to that collection.)</p> <p>The code above seems to work, but somehow doesn't look quite right to me. Questions:</p> <ol> <li>Is observing the Lists collection like this a reasonable approach? It seems like it could be inefficient -- <em>any</em> change to a Lists document will trigger this code.</li> <li>Should I be doing a different (simulated) update client-side, or is it OK to let this same Mongo/Minimongo update run on both?</li> <li>Do I need to call <code>listsObserver.stop()</code> at some point to dispose the observer? And if so, when?</li> </ol> <p>(I'm just getting started with Meteor, so perhaps my biases from other environments are leaking through. The implied meta-question here is, am I even thinking about this problem in the right way?)</p>
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    1. COHmm... just found [this comment](http://stackoverflow.com/a/10463730/647002) in an older question about Meteor data validation. It seems to say you should implement RPC-style Meteor.methods for model editing, and then block the automatic sync of the client's minimongo models back to the server. (Hoping that's not still the recommendation. That automatic, realtime, two-way sync is one of the big attractions of Meteor.)
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