Energy efficient long polling in macOS

Or, more things I encountered when going to macOS from iOS

Making my way to macOS I decided to make a simple status bar app that will check all the movies in iTunes priced at $0.99. You can take quick look here 😘 (go ahead, it’s free). One of my requirements for this app was to make it consume the least amount of power possible, given that in theory will be open 24/7 on someone’s computer.

Sneak peek at the app

In order to do this I looked into iOS equivalents of long polling in macOS, but found something a bit better NSBackgroundActivityScheduler. This class enables you to schedule task in the background repeatedly, which is exactly what I needed in order to constantly check when new deals are available.

NSBackgroundActivityScheduler

The implementation is probably one of the most trivial things I have encountered lately. A single method with a callback, this app is doing something like this:

Beware of race conditions and memory leaks in this schedule block

The only thing that stands out here is the shouldDefer which is just us being a good developer and deferring the execution of this code to a later time (if we can). With that simple block of code the method yourScheduledTask will be called approximately(1) every 4 hours, and then we just handle the block passed to us like so.

That is all 👋. Get in touch on Twitter: @raulriera

Note

(1) While creating this app, it appears that NSBackgroundActivityScheduler is only executed when the computer is connected to a power source. Keep that in mind if you want to schedule really important business logic.