NSString *user = _username.text;
    NSString *password = _password.text;


    AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:[NSURL URLWithString:@"http://thesite.com/login.php"]];
    [httpClient setParameterEncoding:AFFormURLParameterEncoding];
    NSMutableURLRequest *request = [httpClient requestWithMethod:@"POST"
                                                            path:@"http://thesite.com/login.php"
                                                      parameters:@{@"username":user, @"password":password}];
    AFHTTPRequestOperation * httpOperation = [httpClient HTTPRequestOperationWithRequest:request success:^(AFHTTPRequestOperation *operation, id responseObject) {
        //success code
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        //error handler
    }];
    [httpClient enqueueHTTPRequestOperation:httpOperation];

[self performSegueWithIdentifier:@"secondVC"];

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([[segue identifier] isEqualToString:@"secondVC"]) {
    SecondViewController *second = (SecondViewController *)[segue destinationViewController];
    second.userString = self.user;
}
}

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:username forKey:@"UserName"];
[defaults synchronize];

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *username = [defaults objectForKey:@"UserName"];

SecondViewController * sVC = [SecondViewController alloc] initWithUserName: username];

@property (nonatomic, strong) NSString * userName

- (id) initWithUserName: (NSString *) name
{
    self = [super initWithNibName: @"SecondViewController"
                           bundle: nil];
    if (self)
    {
        self.userName = name;
    }
    return self;
}

secondClass *appdelegate = [NSApp delegate];
[appdelegate initwithDetails:userName withPassword:password];

-(id)initwithDetails:(NSString *)user withPassword:(NSString *)password
{
    userName = [NSString stringWithFormat:@"%@", user];
    newPass=[NSString stringWithFormat:@"%@", password];
    return self;
}

#import <Foundation/Foundation.h>

@protocol ProcessDataDelegate <NSObject>
@required
- (void) processSuccessful: (BOOL)success;
@end

@interface ClassWithProtocol : NSObject
{
 id <ProcessDataDelegate> delegate;
}

@property (retain) id delegate;

-(void)startSomeProcess;

@end

#import "ClassWithProtocol.h"

@implementation ClassWithProtocol

@synthesize delegate;

- (void)processComplete
{
  [[self delegate] processSuccessful:YES];
}

-(void)startSomeProcess
{
  [NSTimer scheduledTimerWithTimeInterval:5.0 target:self
    selector:@selector(processComplete) userInfo:nil repeats:YES];
}

@end