UIScrollView with IUViewController dropping objects - iphone

Question

I have a really weird issue with UIScrollView and added UIViewControllers.
It looks like that when UIViewControllers are added to UIScrollView for paging, the UIViewController drops all its added objects.
In the project i have a storyboard with two views and they are connected correctly to the corresponding code.
I know that the code doesn't move the added UIViewController to the correct X, but in this test im only adding one UIViewController so it doesnt matter.
This is the scroll code .h:
#import <UIKit/UIKit.h>
#import "TestViewController.h"
#interface ViewController : UIViewController
#property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
#property (weak, nonatomic) IBOutlet UIPageControl *pageControl;
#property (strong, nonatomic) NSMutableArray *scrollController;
#end
This is the scroll code .m:
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.scrollController = [[NSMutableArray alloc] init];
}
- (void)viewDidAppear:(BOOL)animated {
//just adding two controllers
TestViewController *first = [[TestViewController alloc] init];
[self.scrollView addSubview:first.view];
[self.scrollController addObject:first];
self.scrollView.contentSize = CGSizeMake(self.scrollView.frame.size.width * self.scrollController.count, self.scrollView.frame.size.height);
self.pageControl.numberOfPages = [self.scrollController count];
}
- (void)scrollViewDidScroll:(UIScrollView *)sender {
// Update the page when more than 50% of the previous/next page is visible
CGFloat pageWidth = self.scrollView.frame.size.width;
int page = floor((self.scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
self.pageControl.currentPage = page;
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
This is the viewcontroller code .h:
#import <UIKit/UIKit.h>
#interface TestViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *lblMsg;
#end
This is the viewcontroller code .m:
#import "TestViewController.h"
#interface TestViewController ()
#end
#implementation TestViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
NSLog(#"Label: %#", self.lblMsg);
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
The output in log is:
Label: (null)
Anybody able to see what im doing wrong?

Answer 1

If you create your ViewController using
TestViewController *first = [[TestViewController alloc] init];
your label (IBOutlet) won't be linked.
Navigate to your storyboard in Xcode, select your viewcontroller and assign a unique storyboard id ("myIdentifier") in the identity inspector in utilities on the right hand side.
Try
NSString *identifier = #"myIdentifier";
TestViewController *first = [self.storyboard instantiateViewControllerWithIdentifier:identifier];
Have a look at the documentation:
Each view controller object is the sole owner of its view. You must
not associate the same view object with multiple view controller
objects. The only exception to this rule is that a container view
controller implementation may add this view as a subview in its own
view hierarchy. Before adding the subview, the container must first
call its addChildViewController: method to create a parent-child
relationship between the two view controller objects.