How do I save user preferences for my iPhone app?

Solution 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.

Solution 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.

Solution 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

Solution 4:

You are looking for NSUserDefaults