Gesture triggers exception in subview of UIScrollView - ios

Question

Novice iOS programmer here, so sorry if I'm missing something easy, but...
I have a UIViewController class called LVSTSPMasterViewController whose view was built in IB. The view contains a UIScrollView (added in IB) and that scroll view has a subview of type LVSTSPView. LVSTSPView has a controller of type LVSTSPViewController.
I want to respond to touches in the LVSTSPView, so I added gesture recognizers to LVSTSPViewController.m. When I execute the gesture (e.g., do a long press), the code crashes with message "EXC_BAD_ACCESS (code=1, address=...)" in main.m.
Relevant code:
In LVSAppDelegate.m:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
// Get pointer to app bundle
NSBundle *appBundle = [NSBundle mainBundle];
// Get xib file
LVSTSPMasterViewController *tspmvc = [[LVSTSPMasterViewController alloc] initWithNibName:#"LVSTSPMasterViewController" bundle:appBundle];
self.window.rootViewController = tspmvc;
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
return YES;
}
In LVSMasterViewController.m:
#interface LVSTSPMasterViewController () <UIScrollViewDelegate>
// IBOutlet declarations
#property (nonatomic, weak) IBOutlet UIScrollView *TSPScrollView;
// Pointers for convenience
#property (strong, nonatomic) LVSTSPView *TSPView;
#end
#implementation LVSTSPMasterViewController
- (void)viewDidLoad
{
// Create LVSTSPViewController
LVSTSPViewController *tspvc = [[LVSTSPViewController alloc] init];
// Set up pointer to LVSTSPView
self.TSPView = (LVSTSPView *)tspvc.view;
// Set frame of LVSTSPView
self.TSPView.frame = self.TSPScrollView.bounds;
// Set tspvc's view as subview of TSPScrollView
[self.TSPScrollView addSubview:tspvc.view];
// Set up scroll view
self.TSPScrollView.pagingEnabled = NO;
self.TSPScrollView.contentSize = self.TSPView.frame.size;
self.TSPScrollView.minimumZoomScale = 1.0;
self.TSPScrollView.maximumZoomScale = 3.0;
// Set scroll view's delegate property
self.TSPScrollView.delegate = self;
}
In LVSTSPViewController.m:
- (void)loadView
{
// Create view
LVSTSPView *view = [[LVSTSPView alloc] initWithFrame:CGRectZero];
self.view = view;
// Long-press recognizer
UILongPressGestureRecognizer *pressRecognizer =
[[UILongPressGestureRecognizer alloc] initWithTarget:self action:#selector(longPress:)];
[self.view addGestureRecognizer:pressRecognizer];
}
- (void)longPress:(UIGestureRecognizer *)gr
{
NSLog(#"longPress:");
}
One other note: If I set up the gesture recognizer in viewDidLoad: in LVSTSPMasterViewController.m, like so --
UILongPressGestureRecognizer *pressRecognizer =
[[UILongPressGestureRecognizer alloc] initWithTarget:self action:#selector(longPress:)];
[self.TSPView addGestureRecognizer:pressRecognizer];
-- (and of course add longPress: to LVSTSPMasterViewController.m), then it works. But this doesn't seem like the right approach since the LVSTSPMasterViewController is not the view controller for LVSTSPView.
Any help will be appreciated!

Answer 1

Your view controller LVSTSPViewController is not retained anywhere or in other words your master view controller needs to retain it.
In LVSMasterViewController.m, change your code to
#implementation LVSTSPMasterViewController
{
LVSTSPViewController *tspvc;//creates strong reference to self(LVSTSPMasterViewController)
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
tspvc = [[LVSTSPViewController alloc] init];
// Set up pointer to LVSTSPView
self.TSPView = (LVSTSPView *)tspvc.view;
// Set frame of LVSTSPView
self.TSPView.frame = self.TSPScrollView.bounds;
// Set tspvc's view as subview of TSPScrollView
[self.TSPScrollView addSubview:tspvc.view];
// Set up scroll view
self.TSPScrollView.pagingEnabled = NO;
self.TSPScrollView.contentSize = self.TSPView.frame.size;
self.TSPScrollView.minimumZoomScale = 1.0;
self.TSPScrollView.maximumZoomScale = 3.0;
// Set scroll view's delegate property
self.TSPScrollView.delegate = self;
}
Also always call [super viewDidLoad] first in your viewDidLoad method. I would suggest to read more about view and view controller in the apple documentation. You necessarily do not need a view controller with every view. It all depends on your specific case. One view controller can manage multiple views.