ViewController.m

// 1. Get list of previous contacts from NSUserDefaults
NSMutableArray *previousContacts =
    [[[NSUserDefaults standardUserDefaults] objectForKey:@"contacts"] mutableCopy];
if (!previousContacts) previousContacts = [NSMutableArray array];

// 2. Add new contact to list
self.url = [[Branch getInstance] getShortURLWithParams:@{@"email": self.emailTextField.text}]; // [see note 2]
NSDictionary *newContact = @{ @"name": self.nameTextField.text,
                              @"email": self.emailTextField.text,
                              @"company": self.companyTextField.text,
                              @"url": self.url,
                              @"from": self.currentUsername,
                              @"date": [NSDate date] };
[previousContacts addObject:newContact];

// 3. Save list in NSUserDefaults — TODO: save to robust data store
[[NSUserDefaults standardUserDefaults] setObject:previousContacts forKey:@"contacts"];
[[NSUserDefaults standardUserDefaults] synchronize];