What can cause NSUserDefaults to be cleared - ios

Question

I've been getting some odd reports for my app where the application settings stored into the NSUserDefaults is being cleared. The reports have all been on iOS 7s
I know you can manually clear the NSUserDefaults by either uninstalling or making a call to
NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];
But are there any other known causes for an app to clear its settings ?

Answer 1

If you don't want to get your data deleted, then you should use KeyChain to store values. A good way to get started: Using KeyChain
Below I am providing an example code how to store and get data back from the KeyChain
Importing required frameworks
#import <Security/Security.h>
Storing values to KeyChain
NSString *key = #"Full Name";
NSString *value = #"Steve Jobs";
NSData *valueData = [value dataUsingEncoding:NSUTF8StringEncoding];
NSString *service = [[NSBundle mainBundle] bundleIdentifier];
NSDictionary *secItem = #{
(__bridge id)kSecClass : (__bridge id)kSecClassGenericPassword, (__bridge id)kSecAttrService : service,
(__bridge id)kSecAttrAccount : key,
(__bridge id)kSecValueData : valueData,
};
CFTypeRef result = NULL;
OSStatus status = SecItemAdd((__bridge CFDictionaryRef)secItem, &result);
if (status == errSecSuccess)
{
NSLog(#"Successfully stored the value");
}
else{
NSLog(#"Failed to store the value with code: %ld", (long)status);
}
Getting values back from KeyChain
NSString *keyToSearchFor = #"Full Name";
NSString *service = [[NSBundle mainBundle] bundleIdentifier];
NSDictionary *query = #{
(__bridge id)kSecClass : (__bridge id)kSecClassGenericPassword, (__bridge id)kSecAttrService : service,(__bridge id)kSecAttrAccount : keyToSearchFor,
(__bridge id)kSecReturnAttributes : (__bridge id)kCFBooleanTrue, };
CFDictionaryRef valueAttributes = NULL;
OSStatus results = SecItemCopyMatching((__bridge CFDictionaryRef)query,
(CFTypeRef *)&valueAttributes);
NSDictionary *attributes =
(__bridge_transfer NSDictionary *)valueAttributes;
if (results == errSecSuccess){
NSString *key, *accessGroup, *creationDate, *modifiedDate, *service;
key = attributes[(__bridge id)kSecAttrAccount];
accessGroup = attributes[(__bridge id)kSecAttrAccessGroup]; creationDate = attributes[(__bridge id)kSecAttrCreationDate]; modifiedDate = attributes[(__bridge id)kSecAttrModificationDate]; service = attributes[(__bridge id)kSecAttrService];
NSLog(#"Key = %#\n \ Access Group = %#\n \
Creation Date = %#\n \
Modification Date = %#\n \
Service = %#", key, accessGroup, creationDate, modifiedDate, service);
}
else
{
NSLog(#"Error happened with code: %ld", (long)results);
}