If you've watched the WWDC video you will already know this but if you just look at the class references it isn't obvious that . iOS 8 introduced the possibility to request permission to access location only while the App is in the foreground which should encourage users to grant permission without fear of being tracked inappropriately however the foreground only mode only works with some of the modes. This slide from the talk (WWDC 2014 What's New In Core Location - Session 706) is the key one:

Download LocationAuthorisation-Session706WWDC14.pdf

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I posted about the results of some experiments I had done using the iOS background modes for Bluetooth. At the time I hadn't updated any devices to iOS8 (and they would have been betas anyway). This is a quick update to confirm that there are no changes in these areas that I can see in iOS8.

If you do know of any iOS8 changes or workarounds to the issues described please let me know

Basic Findings (repeated from earlier article)

1. Apps on BLE capable iOS devices can be woken from the background when a device with the correct UUID is detected even when they have been completely removed from memory due to other apps needing the memory.
2. This background listening/advertising state is stopped if the app is deliberately closed by the user swiping it up from the task switcher.
3. The background listening/advertising state is stopped if the device is switched off or runs out of battery. It isn't restarted until the App is run again. (I haven't actually retested running out of battery but am guessing it is the same as manually powering off I will try to test again when the battery on something is getting low)

Please see the previous article for discussion of the impact on on app design and some potential workarounds.

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This is the Swifter Swift presentation I gave at the London Swift Meetup in Clapham today (15th September 2014). Apologies for the stock photos/standard template, I focussed on the content.

I also showed the optimisation levels as described in this blog post.

Things I Forgot To Mention

Use constants - declare with let unless avoidable, allows extra optimisation. Test before changing to mutable state within a function for performance reasons.

Currently the optimiser can do better within a particular file although this will be fixed at some point.

Github Repos

https://github.com/josephlord/GrayScott - Optimised version of Simon Gladwell's Cellular Automata project.

Async.legacy - My iOS7 / OS X 10.9 compatible fork.

Async - Original by Tobias Duemunk

My demo completely failed (Mac locked up when connecting to the projector) so I couldn't show what I wanted. If you want to try the demos yourself these are the Github branches I was going show. All these are 70 pixel square calculations for consistent comparison the main master branch increases in later versions.

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