App Delegate method allowing you to wipe all app data on demand

iOS-resetAppData-in-AppDelegate.m

#define NSDocumentsDirectory()   [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject]
#define NSLibraryDirectory()     [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory,  NSUserDomainMask, YES) firstObject]
#define NSCachesDirectory()      [NSSearchPathForDirectoriesInDomains(NSCachesDirectory,   NSUserDomainMask, YES) firstObject]
//efine NSTemporaryDirectory()   Not needed - defined in Foundation

@implementation AppDelegate

- (void)performDataReset
{
	// Clean-up all data folders...
	NSFileManager *fm = [NSFileManager defaultManager];
	NSArray *folders = @[ NSCachesDirectory(), NSDocumentsDirectory(), NSTemporaryDirectory(), NSLibraryDirectory() ];

	// ...except for some including Crashlytics data
	NSArray *skipped = @[ @"com.crashlytics.data", @"Application Support", @"Caches" ];
	//                         in Caches               in Library         in Library

	NSError *error = nil;
	for (NSString *folder in folders)
		for (NSString *file in [fm contentsOfDirectoryAtPath:folder error:&error])
			if (![skipped containsObject:file])
				[fm removeItemAtPath:[folder stringByAppendingPathComponent:file] error:&error];

	[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:[[NSBundle mainBundle] bundleIdentifier]];
	[[NSUserDefaults standardUserDefaults] synchronize];
}

// Example usage:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
	// Reset application data when selected
	if ([[NSUserDefaults standardUserDefaults] boolForKey:kSettingsResetAppData])
		[self performDataReset];
		
	// ...
}

@end

This peace of code allows to you purge data of your app on launch (filesystem data as well as user defaults).

To clear Crashlytics data as well, simply remove the skipped array and its checking inside for-loop.

Works smoothly on iOS 7+, including both the Simulator and devices.