iphone后台功能执行

- (void)applicationDidEnterBackground:(UIApplication *)application {

__block UIBackgroundTaskIdentifier bgTask;

bgTask = [application beginBackgroundTaskWithExpirationHandler:^{

dispatch_async(dispatch_get_main_queue(), ^{

if (bgTask != UIBackgroundTaskInvalid)

{
bgTask = UIBackgroundTaskInvalid;
}
});
}];

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

dispatch_async(dispatch_get_main_queue(), ^{
NSLog(@"555555");

});

});
}