What is wrong with this attempt to create and populate an NSMutableArray? - iphone

Question

In my .h file, I have:
#property (nonatomic) NSMutableArray *cards;
In my .m file, I have, in the initializer:
- (id) init
{
self = [super init];
self.cards = [NSMutableArray alloc];
return self;
}
In a loop that populates a number of items visible and on-screen:
[self.cards addObject:noteView];
And in a touch event handler, I have:
- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"In touchesBegan.");
UITouch *touch = [touches anyObject];
UIView *selectedView = nil;
CGPoint touchLocation = [touch locationInView:self.view];
for (UIView *card in _cards)
{
CGRect cardRect = [card frame];
NSLog(#"%f", cardRect.origin.x);
NSLog(#"%f", cardRect.origin.y);
NSLog(#"%f", cardRect.size.height);
NSLog(#"%f", cardRect.size.width);
if (CGRectContainsPoint(cardRect, touchLocation)) {
NSLog(#"Match found.");
selectedView = card;
CGRect selectedFrame = selectedView.frame;
selectedFrame.origin.y = -selectedFrame.size.height;
selectedFrame.size = selectedView.frame.size;
float heightRatio = (float) floor([[UIScreen mainScreen] bounds].size.height + .4) / (float) selectedFrame.size.height;
float widthRatio = (float) floor([[UIScreen mainScreen] bounds].size.width + .4) / (float) selectedFrame.size.width;
float ratio = MIN(heightRatio, widthRatio);
selectedFrame.size.height *= ratio;
selectedFrame.size.width *= ratio;
selectedFrame.origin.x = -selectedFrame.origin.x * ratio;
}
}
}
The output for every touch I've made has been that the unconditional NSLog statement is output, but none of the "Log this float" statements execute. It seems that I have not correctly initialized or not correctly populated NSMutableArray.
I seem to get the same behavior whether I refer to _cards or self.cards.
Thanks for any help,
--EDIT--
I seem to be sticking on something else than originally thought of. I now have self.cards = [[NSMutableArray alloc] init], but identical behavior: I go through a loop and populate a bunch of cards, but when I tap one of them, the touch handler outputs "In touchesBegan." but none of the floats. Given an updated init, why would touchesBegan be acting as if it hadn't seen any cards after a number of cards are visible onscreen? (The other output should give a number of lines of floats whether or not the touch was on target for a particular card.)

Answer 1

You need to init the array!
self.cards = [[NSMutableArray alloc] init];
Or
self.cards = [NSMutableArray new];
They are both equivalents
With alloc the only thing you are doing is reserve space in the memory for that variable.
From Apple Documentation:
alloc
Returns a new instance of the receiving class.
init
Implemented by subclasses to initialize a new object (the receiver) immediately after memory for it has been allocated.

Answer 2

Are you using a storyboard for this? Try to initialize your cards property in viewDidLoad.
As a quick check, try to initialize that property right before the loop that is adding objects to it.