I use NSUserDefaults all the time for storing simple users settings and application state.  But there’s a whole lotta string literals and a bunch of repeating yourself that takes place.  That sucks ….

So I like to create a category on NSUserDefaults so I can treat it like a concrete class, whose API is enforced by the compiler and autocompleted by Xcode.  Here’s an example of how I use it to track a users email address within my app.  Note the rcast_ prefix.  Always a good idea to prefix your categories to prevent future name collisions.

//NSUserDefaults_RCastr.h
@interface NSUserDefaults (RCastr)

@property (assign, getter=rcast_userEmail,
           setter=rcast_setUserEmail:) NSString *rcast_userEmail;

//NSUserDefaults_RCastr.m
#import "NSUserDefaults+RCastr.h"
NSString *const rcastDefaultsKeyUserEmail = @"rcast_userEmail";

@implementation NSUserDefaults (RCastr)

#pragma mark -
#pragma mark Username

- (NSString *)rcast_userEmail {
    return [self stringForKey:rcastDefaultsKeyUserEmail];
}

- (void)rcast_setUserEmail:(NSString *)userEmail {
    [self setObject:userEmail forKey:rcastDefaultsKeyUserEmail];
    [self synchronize];
}

@end

That allows me to use user defaults like the following:

    //Set the email address
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    defaults.rcast_userEmail = @"user@domain.com";

    //Get the email address
       NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    if (defaults.rcast_userEmail){
        [FlurryAnalytics setUserID:defaults.rcast_userEmail];
    }

Dead easy change, but much cleaner and far less error prone.

There was a bit of chatter a while back about handling oAuth on the iPhone; in particular security balances sending a user to the website using Safari vs an embedded WebView.  Mike’s blog post discusses this so I won’t repeat, other than to say that I think either solution (webView or Safari) is open for spoofing.  An app developer could spoof an auth and grab creds in either case pretty easily … so I’ve chosen to optimize for user experience by implemented an oAuth webView for our app.

Here’s some of the relevant code for launching to an authorize website and handling the response.

* Our app uses oAuthConsumer library

* Our implimentation was against linkedin oauth which meant that I needed to pass the oauth_callback in our request token request by setting the oauth_callback parameter there rather than the authorize URL

In other words, our requestToken method looks something like the following:

OAMutableURLRequest                *request = [[[OAMutableURLRequest alloc] initWithURL: self.requestTokenURL consumer: self.consumer token:nil realm:nil signatureProvider: nil] autorelease];
 if (!request) return;
 [request setHTTPMethod: @"POST"];
 [request setParameters: [NSArray arrayWithObject: [[[OARequestParameter alloc] initWithName: @"oauth_callback" value: kLinkedInCallbackUrl] autorelease]]];
 OADataFetcher                *fetcher = [[[OADataFetcher alloc] init] autorelease];
 [fetcher fetchDataWithRequest: request delegate: self didFinishSelector: @selector(setRequestToken:withData:) didFailSelector: @selector(outhTicketFailed:data:)];

With the request token set, we’re able to pass this to the authorize url and it will return to our custom url

/*Create the request object for the linkedin URL*/

if (!_requestToken.key && _requestToken.secret) return nil;    // we need a valid request token to generate the URL

 OAMutableURLRequest            *request = [[[OAMutableURLRequest alloc] initWithURL: self.authorizeURL consumer: nil token: _requestToken realm: nil signatureProvider: nil] autorelease];

 [request setParameters: [NSArray arrayWithObject: [[[OARequestParameter alloc] initWithName: @"oauth_token" value: _requestToken.key] autorelease]]];

/*Load the webview with this request*/

[_webView loadRequest: request];

/*Check the response for a custom uri and redirect if it's set*/
- (BOOL) webView: (UIWebView *) webView shouldStartLoadWithRequest: (NSURLRequest *) request navigationType: (UIWebViewNavigationType) navigationType {
 NSData                *data = [request HTTPBody];
 char                *raw = data ? (char *) [data bytes] : "";
 NSURL* url = request.URL;

 if ([url.scheme isEqualToString:@"liconnect"]) {
 [_spinner stopAnimating];
 if ([url.resourceSpecifier isEqualToString:@"cancel"]) {
 if ([_delegate respondsToSelector:@selector(OAuthLinkedInAuthorizeViewFailed:)]) {
 [_delegate OAuthLinkedInAuthorizeViewFailed:self];
 }
 }
 else {
 [self dialogDidSucceed:url];
 }

 return NO;
 }

 if (raw && strstr(raw, "cancel=Deny")) {
 [self denied];
 return NO;
 }
 if (navigationType != UIWebViewNavigationTypeOther) _webView.alpha = 0.1;
 return YES;
}

/*Strip out the token and auth_verifier from the url*/

- (void)dialogDidSucceed:(NSURL*)url {
 NSString* q = url.query;
 NSLog(q);
 NSRange verifier_start = [q rangeOfString:@"oauth_verifier="];

 NSRange start = [q rangeOfString:@"auth_token="];
 if (start.location != NSNotFound) {
 NSRange end = [q rangeOfString:@"&"];
 NSUInteger offset = start.location+start.length;
 NSString* token = end.location == NSNotFound
 ? [q substringFromIndex:offset]
 : [q substringWithRange:NSMakeRange(offset, end.location-offset)];

 NSString* verifier = [q substringFromIndex:verifier_start.location+verifier_start.length];
 if (token&&verifier) {
 if ([_delegate respondsToSelector:@selector(requestTokenReceived:withVerifier:)]){
 [_delegate requestTokenReceived:token withVerifier:verifier];
 }
 }
 else
 {
 if ([_delegate respondsToSelector:@selector(OAuthLinkedInAuthorizeViewFailed:)]){
 [_delegate OAuthLinkedInAuthorizeViewFailed:self];
 }        }
 [self removeFromSuperview];
 }
}

You’re done.  You’ve now got your oauth_verifier and your access token all lined up to store away or make immediate calls to the api.