UILabel doesn't update through modal presentation view controller

Question

I have two class, PresentViewController and ModalViewController , In PresentViewController I call the ModalViewController in this format:

ModalViewController *targetController = [[ModalViewController alloc] init];

targetController.modalPresentationStyle = UIModalPresentationFormSheet;

targetController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

[self presentViewController:targetController animated:YES completion:nil];

// it is important to do this after presentModalViewController:animated:
targetController.view.superview.bounds = CGRectMake(0, 0, 400, 218);

In ModalViewController , I have a button who send a parameter to the class PresentViewController :

-(IBAction)apply{

    PresentViewController *infoViewController = [[PresentViewController alloc] init];
    [infoViewController setDiscount:[campoDesconto.text intValue]];

        [self dismissViewControllerAnimated:YES completion:nil];

}

In PresentViewController the method setDiscount is as follows:

-(void)setDiscount:(int)value{

    NSLog(@"Method is called!");
    totalPrice.text = value;

}

This method is being called because I get a console message, but unfortunately this UILabel not updating your value, why this is happening and how can I solve?

Answer 1

That's because totalPrice is not probably instantiated before setDiscount: is called. Call setDiscount: after your view is loaded and totalPrice is instantiated to have the label text updated.

Answer 2

When you call apply method, you haven't setup the view of infoViewController yet. So you probably haven't created the totalPrice label yet, if you do NSLog(@"totalPrice: %@", totalPrice); in setDiscount: , it will probably output (null) . You should save the discount value as a property, and set it in viewDidLoad as well as when setDiscount: method is called.

You're also setting an int to a NSString , this isn't correct.

PresentViewController.h

@interface PresentViewController : UIViewController

@property (nonatomic, assign) int discount;

@end

PresentViewController.m

@implementation PresentViewController

-(void)viewDidLoad
{
    [super viewDidLoad];

    // Setup detailLabel

    detailLabel.text = [@(self.discount) stringValue];
}

-(void)setDiscount:(int)discount
{
    _discount = discount;
    detailLabel.text = [@(_discount) stringValue];
}

@end