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POUnderstanding and writing singleton class instead of using delegate class
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  1. POUnderstanding and writing singleton class instead of using delegate class
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    copied!<p>I'm new in iOS programming and I am very interested in what singleton class is, and why it is used. I found some information but it is vague. In particular I would like to apply it to real example. My project use Facebook SDK and I want to create singleton class for my NSDictionary which contain friends list. My .m delegate file:</p> <pre><code>- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { //here is some other code facebook = [[Facebook alloc] initWithAppId:@"my app id" andDelegate:self]; NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; if ([defaults objectForKey:@"FBAccessTokenKey"] &amp;&amp; [defaults objectForKey:@"FBExpirationDateKey"]) { facebook.accessToken = [defaults objectForKey:@"FBAccessTokenKey"]; facebook.expirationDate = [defaults objectForKey:@"FBExpirationDateKey"]; } if (![facebook isSessionValid]) { NSArray *permissions = [[NSArray alloc] initWithObjects: @"user_location", @"friends_location", @"read_friendlists", nil]; [facebook authorize:permissions]; [permissions release]; } [facebook requestWithGraphPath:@"me/friends" andDelegate:(id)self]; //here is some other code } </code></pre> <p>And I set to my NSDictionary value of request which return friends list:</p> <pre><code>- (void)request:(FBRequest *)request didLoad:(id)result { _friendsDictionary = result; } </code></pre> <p>In which way I need to write singleton class and do not use delegate class <code>AppDelegate *delegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];</code>.</p>
 

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