How to detect if the device has just been rebooted? - ios

Question

I have and application which give data usage in intervals. I want to detect if the device has been rebooted before using the data usage. I tried using mach_absolute_time() but i could not understand anything.Is it possible?

Answer 1

You can get the system uptime like this:
let systemUptime = NSProcessInfo.processInfo().systemUptime; // swift
NSTimeInterval timeInterval = [NSProcessInfo processInfo].systemUptime; //Objective c
You can store it in NSUserDefaults and use it to determine if a reboot occurred.
Please also check this thread for more information.
Swift 3:
let systemUptime: TimeInterval = ProcessInfo.processInfo.systemUptime

Answer 2

Here is one I made. It takes the current time in GMT and the time since last reboot to extrapolate a date for when the device was last restarted. Then it keeps track of this date in memory using NSUserDefaults. Enjoy!
#define nowInSeconds CFAbsoluteTimeGetCurrent()//since Jan 1 2001 00:00:00 GMT
#define secondsSinceDeviceRestart ((int)round([[NSProcessInfo processInfo] systemUptime]))
#define storage [NSUserDefaults standardUserDefaults]
#define DISTANCE(__valueOne, __valueTwo) ((((__valueOne)-(__valueTwo))>=0)?((__valueOne)-(__valueTwo)):((__valueTwo)-(__valueOne)))
+(BOOL)didDeviceReset {
static BOOL didDeviceReset;
static dispatch_once_t onceToken;
int currentRestartDate = nowInSeconds-secondsSinceDeviceRestart;
int previousRestartDate = (int)[((NSNumber *)[storage objectForKey:#"previousRestartDate"]) integerValue];
int dateVarianceThreshold = 10;
dispatch_once(&onceToken, ^{
if (!previousRestartDate || DISTANCE(currentRestartDate, previousRestartDate) > dateVarianceThreshold) {
didDeviceReset = YES;
} else {
didDeviceReset = NO;
}
});
[storage setObject:#(currentRestartDate) forKey:#"previousRestartDate"];
[storage synchronize];
return didDeviceReset;
}