How do I save user preferences for my iPhone app? - ios

Question

The question title pretty much gives it away - I'd like my app to remember a few things. It's some sort of calculator, so it should save the last used values and some user selectable settings.
Basically I'd like to save a handful of floats and BOOLs and load them again the next time the app loads.
What's the best and easiest way to do that?
Thanks!!

Answer 1

One of the easiest ways would be saving it in the NSUserDefaults:
Setting:
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
[userDefaults setObject:value
forKey:key];
// – setBool:forKey:
// – setFloat:forKey:
// in your case
[userDefaults synchronize];
Getting:
[[NSUserDefaults standardUserDefaults] objectForKey:key];
– boolForKey:
and
– floatForKey: in your case.

Answer 2

Besides the very good NSUserDefaults approach, there is another easy way to store data from an NSArray,NSDictionary or NSData in a file. You can use these methods as well:
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)flag
respectively (for a NSDictionary):
+ (id)dictionaryWithContentsOfFile:(NSString *)path
you just have to give a valid path to a location. According to the iOS Application Programming Guide, the /Library/Caches directory would be the best place to store data that you need to persist between app launches. (see here)
In order to store/load a dictionary from a filed called "managers" in your document directoy you could use these methods:
-(void) loadDictionary {
//get the documents directory:
NSArray *paths = NSSearchPathForDirectoriesInDomains (NSCachesDirectory, NSUserDomainMask, YES);
NSString *cacheDirectory = [paths objectAtIndex:0];
//create a destination file name to write the data :
NSString *fullFileName = [NSString stringWithFormat:#"%#/managers", cacheDirectory];
NSDictionary* panelLibraryContent = [NSDictionary dictionaryWithContentsOfFile:fullFileName];
if (panelLibraryContent != nil) {
// load was successful do something with the data...
} else {
// error while loading the file
}
}
-(void) storeDictionary:(NSDictionary*) dictionaryToStore {
//get the documents directory:
NSArray *paths = NSSearchPathForDirectoriesInDomains
(NSCachesDirectory, NSUserDomainMask, YES);
NSString *cacheDirectory = [paths objectAtIndex:0];
//make a file name to write the data to using the
//cache directory:
NSString *fullFileName = [NSString stringWithFormat:#"%#/managers", cacheDirectory];
if (dictionaryToStore != nil) {
[dictionaryToStore writeToFile:fullFileName atomically:YES];
}
}
Anyway this approach is very limited and you have to spend a lot of extra work if you want to store more complex data. In that case the CoreData API is very very handy.

Answer 3

In Swift:
Setting
let userDefaults = NSUserDefaults.standardUserDefaults()
userDefaults.setObject(value, forKey: key)
// userDefaults.setFloat(12.34, forKey: "myFloatKey")
// userDefaults.setBool(true, forKey: "myBoolKey")
Note that for iOS 8 and later, calling userDefaults.synchronize() is not recommended.
Getting
let userDefaults = NSUserDefaults.standardUserDefaults()
if let value = userDefaults.objectForKey(key) {
print(value)
}
Note that userDefaults.boolForKey and userDefaults.floatForKey both return non optional values, so they would never be nil (only false or 0.0).
Further reading
NSUserDefaults — A Swift Introduction

Answer 4

You are looking for NSUserDefaults

Answer 5

Swift 4 / Linux
Apparently something has changed. Now there's the UserDefault class.
Check these links:
https://developer.apple.com/documentation/foundation/userdefaults
https://www.hackingwithswift.com/read/12/2/reading-and-writing-basics-userdefaults