user credential persistence in iPhone

Question

Hi Guys, Since i'm new to iPhone programming, I want to do something like that: In the main screen of my app, i ask for username and password and authorize user using these info calling .net web service. In this main screen, there is a switch controller "Remember me" so that app will remember the user next time he run the app. My questions are: 1. how can i call .net web services in iPhone? 2. how can i persist these username and password information (like cookie in web app), so that user will not be asked for credential info? i would really appreciate, thanks.

Answer 1

1. you use nsmutableurlrequest to generate a web services request
2. use nsuserdefaults to persist the username and password

Here's an example of the first:

-(void)sendUpdate {

    User *user = [User sharedManager];

    NSData *parkedLocation = [[NSString stringWithFormat:@"<location><latitude>%f</latitude><longitude>%f</longitude><userid>%@</userid><udid>%@</udid></location>", 
             coordinate.latitude, coordinate.longitude, userid, user.udid] dataUsingEncoding:NSASCIIStringEncoding];
    //NSLog("parkedlocation = %@", parkedLocation);
    NSString *URLstr = LOCATIONS_URL;
    if (controller.put_url) 
     URLstr = controller.put_url;
    NSURL *theURL = [NSURL URLWithString:URLstr];
    //NSURLRequest *theRequest = [NSURLRequest requestWithURL:theURL cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.0];
    NSLog(@"IN SEND UPDATE put_url = %@", controller.put_url);

    NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:theURL cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.0];
    if (controller.put_url) {
     [theRequest setHTTPMethod:@"PUT"];
    } else {
     [theRequest setHTTPMethod:@"POST"];
    }
    [theRequest setValue:@"text/xml" forHTTPHeaderField:@"Content-type"];
    [theRequest setHTTPBody:parkedLocation];

    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:TRUE];

    NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

    if (!theConnection) {
     NSLog(@"COuldn't get a connection to the iParkNow! server");
    }
}

and an example of the second:

 [[NSUserDefaults standardUserDefaults] setObject:self.userName.text forKey:@"Username"];
     [[NSUserDefaults standardUserDefaults] setObject:self.password.text forKey:@"Password"];

Answer 2

You have two choices: User Preferences or Core Data. Both are capable - Core Data might be overkill.

Answer 3

NSURLRequest can be used to retrieve URLs such as your authentication service. And NsUserDefaults can be used to save settings in between app invocations.

Note: Check out ennuikiller's awesome example.

Answer 4

Persisting user credentials

If you are storing a username and password you should use the Keychain. Using the Keychain on iPhone is analogous to Keychain on the Mac.

To use Keychain import "Security/Security.h".

Apple has an example here of adding and retrieving a username and password in their documentation. The example methods

    - (void)mySetObject:(id)inObject forKey:(id)key;
    - (id)myObjectForKey:(id)key;
    - (void)resetKeychainItem;

will enable you to persist and retrieve your user credentials almost without modifying the example code.

Calling webservices that require authentication

Depending on you authentication scheme you can either

• provide username and password directly as parameters in the URL using NSURLConnection
• provide a didReceiveAuthenticationChallenge method in your NSURLConnection delegate if your webservice use the "Basic Authentication" scheme