Question

I have a UILabel that I would like to update. It has been added to the class by ctrl-cicking and adding through the XIB file. Im trying to update the label text after waiting for a short delay. As of now, there is nothing else going on except for the code below. Howver when I run this, the simulator blanks out for a moment and takes me straight to the last updated text. It doesnt show me the 100 just the 200.

How do I get the label to update like I want it to. Ultimately Im trying to have a timer of sorts decrement inside the label.

Label linked from the XIB to header file:

@property (strong, nonatomic) IBOutlet UILabel *timeRemainingLabel;

In Implmentation:

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.timeRemainingLabel.text = @"100";
    sleep(1);
    self.timeRemainingLabel.text = @"200";    
}

• It has been synthesized.

• XCode 4.3.2, Mac OSX 10.7.3, iOS Simulator 5.1 (running iPad), iOS 5

Answer 1

The problem with your implementation is that the execution sequence does not leave the method while in the sleep. This is the problem, because the UI subsystem never gets a chance to update the label to the "100" value before it gets a command to set it to "200".

To do this correctly, first you need to create a timer in your init method, like this:

timer = [NSTimer scheduledTimerWithTimeInterval: 1.0 target:self selector:@selector(updateLabel) userInfo:nil repeats: YES];

Then you need to write the code for your updateLabel method:

-(void) updateLabel {
    NSInteger next = [timeRemainingLabel.text integerValue]-1;
    timeRemainingLabel.text = [NSString stringWithFormat:@"%d", next];
}