Question

I’m trying to create a simple Quiz app (I’m a beginner), when I launch the app I want a UILabel to show the first question (of an array of questions). I’m having some trouble with setting the initial value.

I’ve done a couple of attempts, whiteout success. I my QuizAppDelegate.h file I declare my UILabel like this:

 IBOutlet UILabel * questionField;

In my main .m file I have tried the following:

- (id)init {

    [super init];

    questions = [[NSMutableArray alloc] init];

    // Not working
    questionField = [[UILabel alloc] init];
    [questionField setText:@"Hello"];

    // Working
    NSLog(@"Hello");

    [self defaultQuestions];
    // [self showQuestion];

    return self;
}

Another thing I have tried is the following in QuizAppDelegate:

@property (nonatomic, retain) IBOutlet UILabel *questionField;

- (void)changeTitle:(NSString *)toName;

And in the .m file:

@synthesize questionField;

- (id)init {

    [super init];

    questions = [[NSMutableArray alloc] init];

    // Not working
    [self changeTitle:@"Hello"];

    // Working
    NSLog(@"Hello");

    [self defaultQuestions];
    // [self showQuestion];

    return self;
}

-(void)changeTitle:(NSString *)toName {
    [questionField setText:toName];
}

Any tips on how to solve this would be great!

// Anders

Answer 1

Hopefully you’re not actually putting code into main.m. On iOS, you rarely modify that file.

Since you’re doing everything in the AppDelegate, let’s keep it there (as opposed to creating a new UIViewController). Let’s start with the basics.

Adding the Label as an instance variable

You’re doing this correctly—inside the curly braces of the .h file, put the line

IBOutlet UILabel * questionField;

Then, declare the corresponding property, and make sure to synthesize it in the .m file.

@property (nonatomic, retain) IBOutlet UILabel *questionField;
@synthesize questionField    // in the .m file

---

Adding the UILabel in Interface Builder

Open up MainWindow.xib. Drag a UILabel from the Library to the Window that represents your app’s window. Then Control-Drag from the AppDelegate object (the third icon on the left in Xcode 4; it’ll be labelled in the Document window in IB 3). You’ll see a little black window come up—select the option called questionField to make the connection.

See this link for screenshots and how to make connections in IB. The same applies in Xcode 4.

---

Changing the text

You don’t need a separate method to change the text—just modify the label’s text property.

Pick a method that’ll be called when the app launches (applicationDidFinishLaunching:WithOptions: is a good place to do it in), and put the following code:

questionField.text = @"Hello";

And that’s it!

---

Code

QuizAppDelegate.h

#import <UIKit/UIKit.h>

@interface QuizAppDelegate : NSObject <UIApplicationDelegate> {
    IBOutlet UILabel *questionField;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UILabel *questionField;

@end

QuizAppDelegate.m

#import "QuizAppDelegate.h"

@implementation QuizAppDelegate

@synthesize window=_window;
@synthesize questionField;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    // Add the tab bar controller's current view as a subview of the window
    [self.window addSubview:self.questionField];
    [self.window makeKeyAndVisible];
    self.questionField.text = @"Hello";
    return YES;
}

- (void)dealloc
{
    [_window release];
    [questionField release];
    [super dealloc];
}

@end