Obj-C UIImageView not showing image from NSArray - ios

Question

I am doing a little self learning with Obj-c and interested in making a flash card application. I have an NSArray with objects with 5 images in the array. When the user presses the forward button I am trying to get my UIImageView to show the next image in the array. I get Thread 1: EXC_BAD_ACCESS(Code=2,address=0x0) on the line where I get an image from my array. Here is my current header and implementation file.
#interface WhoAmIViewController : UIViewController
#property (strong, nonatomic) IBOutlet UIImageView *flashcardviewer;
#property (strong, nonatomic) NSArray *aryFlashcards;
#property (nonatomic) NSUInteger *int_counter;
#end
#implementation WhoAmIViewController
#synthesize aryFlashcards;
#synthesize flashcardviewer;
#synthesize int_counter;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
aryFlashcards = [NSArray arrayWithObjects:
[UIImage imageNamed:#"shot_1"],
[UIImage imageNamed:#"shot_2"],
[UIImage imageNamed:#"shot_3"],
[UIImage imageNamed:#"shot_4"],
[UIImage imageNamed:#"shot_5"],
nil];
int_counter = 0;
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
//back button
- (IBAction)btn_back:(UIButton *)sender {
}
//forward button
- (IBAction)btn_forward:(UIButton *)sender
{
flashcardviewer = [[UIImageView alloc]init];
UIImage *flashcard_next = [UIImage imageNamed:[aryFlashcards objectAtIndex:*(int_counter)]]; //This is where Xcode throws me an error.
flashcardviewer.image = flashcard_next;
int_counter++;
}
//random button
- (IBAction)btn_random:(UIButton *)sender
{
}

Answer 1

You made int_counter a pointer instead of an NSInteger. Try
#property (nonatomic) NSUInteger int_counter;
and
UIImage *flashcard_next = [aryFlashcards objectAtIndex:int_counter];

Answer 2

Try the following code:
//Declare int_counter like this
#property (nonatomic) NSUInteger int_counter;
//Set btn_forward: this way
- (IBAction)btn_forward:(UIButton *)sender
{
//Avoid possible app crash with a if condition
if (int_counter < flashcard_next.count) {
UIImage *flashcard_next = [aryFlashcards objectAtIndex:int_counter];
flashcardviewer.image = flashcard_next;
int_counter++;
} else {
NSLog (#"No more cards");
}
}
You can learn more about NSInteger here.

Answer 3

Your problem is on this line:
UIImage *flashcard_next = [UIImage imageNamed:[aryFlashcards objectAtIndex:*(int_counter)]];
You're creating a UIImage object and passing another UIImage to the method when it's expecting a NSString. Change this to:
UIImage *flashcard_next = [aryFlashcards objectAtIndex:int_counter];
and as mentioned in the other answer, remove the pointer to int_counter.

Answer 4

Your iVar aryFlashcards is already instantiated with 5 images in viewDidLoad method. In your btn_forward method implementation you should replace
UIImage *flashcard_next = [UIImage imageNamed:[aryFlashcards objectAtIndex:*(int_counter)]];
With following provided *(int_counter) is less than aryFlashCards size which looks to be 5 in your example else your app will throw out of bound exception.
UIImage *flashcard_next = [aryFlashcards objectAtIndex:*(int_counter)];