Awesome feature of the day, RavenDB Changes API
This was a really hard feature. I’ll discuss exactly why and how in my next post, but for now, I pretty much want to gloat about this. We now have the ability to subscribe to events from the server on the client.
This opens up some really nice stories for complex apps, but for now, I want to show you what it does:
store.Changes() .DocumentSubscription("orders/1293") .Subscribe(Reload);
You can add subscribe to multiple documents (or even all documents) and you can also subscribe to changes in indexes as well.
Why is this an awesome feature? It opens up a lot of interesting stories.
For example, let us assume that the user is currently editing an order. You can use this feature to detect, at almost no cost, when someone have changed that order, saving the user frustration when / if he tries to save his changes and get a concurrency exception.
You can also use this to subscribe to a particular index and update in memory caches on update, so the data is kept in memory, and you don’t have to worry about your cache being stale, because you’ll be notified when it does and can act on this.
You can even use this to watch for documents of a particular type coming in and do something about that. For example, you might setup a subscription for all alerts, and whenever any part of the system writes a new alert, you will show that to the user.
The last one, by the way, is a planned feature for RavenDB Studio itself. As well as a few others that I’ll keep hidden for now .