CODEWITHSUNDEEP
c#iosxamarin.iosmonodevelopnsuserdefaults
iLemming
iLemming

Reputation: 36214

NSUserDefaults.StandardUserDefaults - saving and retrieving a Dictionary

Would you guys help me? I found how to save and retrieve simple objects to use them as app settings.

NSUserDefaults.StandardUserDefaults.SetString("testUser","username");
NSUserDefaults.StandardUserDefaults.Init(); //Although it's strange that you have to call this method to actually save your stuff

and later you can retrieve it like that:

var username = NSUserDefaults.StandardUserDefaults.StringForKey("username");

Now, what if I need to save multiple usernames (as many as I want)? And what if I need to save multiple usernames with passwords or passhashes?

Upvotes: 11

Views: 7086

Answers (3)

Jay Imerman
Jay Imerman

Reputation: 4600

I had trouble getting NSUserDefaults to store dictionaries. What I ended up doing, is simply obtaining the Documents directory, and saving my dictionary to a file when the app is terminating or going to the background, then loading it from a file when the app finishes loading. NSDictionary and NSMutableDictionary have class methods that load or save from a file - and it uses serialized XMLs, so it's nice and elegant.

This is good if your app doesn't need a large amount of data, and the data is simple and structure is fluid.

Upvotes: 1

poupou
poupou

Reputation: 43553

Here's an example for arrays (many strings kept with a single key):

        NSUserDefaults.StandardUserDefaults ["array"] = NSArray.FromStrings ("a", "b", "c");
        foreach (string s in NSUserDefaults.StandardUserDefaults.StringArrayForKey ("array")) {
            Console.WriteLine (s);
        }

And an example where a dictionary (key=value) is kept with a single key:

        NSDictionary dict = NSDictionary.FromObjectsAndKeys (new object[] { "user1", "user2" }, new object[] { "123", "abc" });
        NSString key = new NSString ("dict");
        NSUserDefaults.StandardUserDefaults.SetValueForKey (dict, key);
        NSDictionary d2 = NSUserDefaults.StandardUserDefaults.DictionaryForKey (key);
        for (int i = 0; i < d2.Count; i++) {
            Console.WriteLine ("{0} : {1}", d2.Keys [i], d2.Values [i]);
        }

Upvotes: 12

huesforalice
huesforalice

Reputation: 2458

I would consider using core-data if you have a lot of users you also want to search for and filter. If your app is not that complex, you can always serialize a dictionary into a string and save it as such in the user defaults. A good library for JSON (de)serialization is SBJSON http://stig.github.com/json-framework/.

Upvotes: 1

Related Questions