iphone hello world

HelloWorldViewController.h

#import <UIKit/UIKit.h>

@interface HelloWorldViewController : UIViewController <UITextFieldDelegate>
@property (copy, nonatomic) NSString *userName;

@end

HelloWorldViewController.m

#import "HelloWorldViewController.h"

@interface HelloWorldViewController ()
@property (weak, nonatomic) IBOutlet UITextField *textField;
- (IBAction)changeGreeting:(id)sender;
@property (weak, nonatomic) IBOutlet UIButton *label;

@end

@implementation HelloWorldViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)changeGreeting:(id)sender {
    self.userName = self.textField.text;
    
    NSString *nameString = self.userName;
    if ([nameString length] == 0) {
        nameString = @"World";
    }
    
    NSString *greeting = [[NSString alloc] initWithFormat:@"Hello, %@!", nameString];
    [self.label setTitle:greeting forState:UIControlStateNormal];
    
}

- (BOOL)textFieldShouldReturn:(UITextField *)theTextField {
    if (theTextField == self.textField) {
        [theTextField resignFirstResponder];
    }
    return YES;
}

@end