“Variable Undeclared” error when compiling to iOS Device, but not for Simulator

Question

I have an custom UIVIewController that is the base class for other controllers and has an instance of a custom UIView variable that is accessed by inherited the classes.

Answer 1

I just stumble upon your method declaration

-(void)loadView { ... }

In a view the first point you can rely that everything is fully initialized is after -(void)viewDidLoad was called. Maybe your code works on the simulator because your Mac is fast enough to cope this speed issue - but your mobile device isn't.

Maybe try this coding:

Your BaseViewController.h file:

@interface BaseViewController : UIViewController {
    UIView *_vwHeader;
}
@end

Your BaseViewController.m file:

#import "BaseViewController.h"
@implementation BaseViewController

-(void)viewDidLoad {
    [super viewDidLoad];
    _vwHeader = [[UIView alloc] init];
}

Your CustomViewController.h file:

@interface CustomViewController : BaseViewController {
}
@end

Your CustomViewController.m file:

#import "CustomViewController.h"

-(void)viewDidLoad {
    [super viewDidLoad];
    [_vwHeader setHidden:NO];
}

Now your CustomViewController can rely on every instance variable in BaseViewController is correctly instantiated.

Answer 2

I had this exact problem.

In my case, I was relying on ivar synthesis of a property. That is, I did NOT declare UITextView *textView_, but I did @synthesize textView = textView_;

This builds fine on my iOS Simulator. However, my iOS device build fails, regardless of whether I use llvm or gcc.

When I add the declaration back to my interface:

@interface MyTableViewController : BaseTableViewController {
    @private
    UITextView *textView_; // this line is important!
}

Everything works fine!

Answer 3

See the answer from tc above. This is a bug in the compiler shipped with sdk 4.2. Specifically I have seen the same error and if on the same machine I have sdk 4.2 and sdk 4.3 installed the error disappears (even if I compile for 4.2).

Answer 4

Do a clean and build, and also make sure you are not specifying a specific framework search path in the build settings. If you leave it empty you should get the correct libraries. well I don't know, should work.

BaseViewController.h

@interface BaseViewController : UIViewController {
    UIView *_vwHeader;
}
@property(nonatomic,retain)UIView *_vwHeader;
@end

BaseViewController.m

@synthesize _vwHeader;

CustomViewController.m

#import "CustomViewController.h"
@implementation CustomViewController

- (void)loadView
{
    [super loadView];

    [self._vwHeader setHidden:NO];
}

@end

Answer 5

The error says that _vwHeader undeclared. So try by modifying the code in:

CustomViewController.m

    #import "CustomViewController.h"
    @implementation CustomViewController

    - (void)loadView
    {
        [super loadView];
        if(!_vwHeader)
        {
           _vwHeader = [[UIView alloc]init];
        }
        [_vwHeader setHidden:NO];
    }

    @end

Answer 6

In order to refer to an instance variable within any object other than self, including super, you must use the structure pointer operator (->). The default scope of an instance variable is protected, which means it can only be accessed within the class it is defined in or a subclass of that class. Since CustomViewController is a subclass of BaseViewController, this scope is sufficient to access the variable using self->_vwHeader, but if the second class you were trying to do this from is not a subclass you will also need to change the scope to either @public or @package.

In summary, change your method call to:

[self->_vwHeader setHidden:NO];

and it should work for any subclasses of the base view controller.