Use didFinishLaunchingWithOptions to save preferences - ios

Question

there is a notification in my view controller that listens for preference changes and then updates the sound settings. When I change the sound settings and then kill the app, the prefs don't persist.
I need to check those prefs and set the sounds settings based on the persisted prefs on app launch
Can I do this from the app delegate, if so, how?
Here is the notification
- (void)preferencesDidChange:(NSNotification *)note
{
NSMutableArray *changedPreferences = note.object;
if ([changedPreferences containsObject:#"localPlayUISounds"]) {
[FHSSound setUISoundsEnabled:PREFS.localPlayUISounds];
}
else if ([changedPreferences containsObject:#"localPlayAlertSounds"]) {
[FHSSound setAlertSoundsEnabled:PREFS.localPlayAlertSounds];
}
else if ([changedPreferences containsObject:#"localEnablesDNDWhenDrivingCar"]) {
[self startMonitoringLocationIfEnabled];
}
}

Answer 1

I would use NSUserDefaults for this.
The system keeps a set of defaults for your app. You just have to add the values when they are set, and load them again in didFinishLaunchingWithOptions.
To save a value, when the user changes it:
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setBool:YES forKey:#"playSound"];
[defaults synchronize];
To load it at startup (in the app delegate):
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
bool playSound = [userDefaults boolForKey:#"playSound"];
One extra detail: on the first run of the app those values will return NO, so you want to detect that.
I would do something like this on the app delegate:
int runCount = (int)[userDefaults integerForKey:#"runCount"];
if (!runCount)
{
//first run, save the predefined values
}
else
{
//not first run, load the previously saved values
}
runCount++;
[userDefaults setInteger:runCount forKey:#"runCount"];

Answer 2

Take a look at this answer about saving user preferences.
Once your preferences are persisted, then you can reload them whenever the application starts by providing your own implementation of
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
You might also consider registering a handler for the UIApplicationDidBecomeActiveNotification event if you want to restore the sound settings whenever the application returns to the foreground even if it wasn't killed between activations.

Answer 3

The data was already persisting, I just had to find a way for the app to launch off of the persisted data. Here is what I did
- (void)viewDidLoad
{
[super viewDidLoad];
[self setSoundPreferences];
}
The notification is set to listen for the change in prefs
- (void)preferencesDidChange:(NSNotification *)note
{
NSMutableArray *changedPreferences = note.object;
if ([changedPreferences containsObject:#"localPlayUISounds"]) {
[FHSSound setUISoundsEnabled:PREFS.localPlayUISounds];
}
else if ([changedPreferences containsObject:#"localPlayAlertSounds"]) {
[FHSSound setAlertSoundsEnabled:PREFS.localPlayAlertSounds];
}
and lastly setting the preferences at launch
#pragma mark (launch)
- (void)setSoundPreferences
{
[FHSSound setUISoundsEnabled:PREFS.localPlayUISounds];
[FHSSound setAlertSoundsEnabled:PREFS.localPlayAlertSounds];
}