ios后台服务以计算距离并通知用户

Question

I'm using ios mapkit for my project. Basically, I'm trying to notify the user when he arrives at a given location. What I do here is I get the distance to the destination and if it's somewhere around 20 meters I'm calling a REST API which will send a push notification to another user. This works fine if the app in the foreground. But how can I do this while the app is in the background? I know there are background modes in the ios. But I can't figure out which mode going to fit here

Thanks

Answer 1

Having tested and deployed region monitoring in production code, I can tell you its bad for walking. It relies on cell towers and the alerts are very flakey at fence sizes of less that 150-200 meters, which is a long way to walk. We initially tried 30 meters and the results were disastrous with tons of false negatives and a few false positives. If you really want to detect 20 meters then you need to use GPS mode, which is drains the battery but its the only thing that has that kind of granularity.