Question

In one class, I define an NSMutableArray with getters and setters:

@interface ArrayClass : NSObject {
    NSMutableArray *array;
}
@property (nonatomic, strong) NSMutableArray *array;

@end

Then within the implementation file, I alloc init the mutable array:

#import "ImageUploader.h"

@implementation ArrayClass
@synthesize array;

- (id)init {
    self = [super init];
    if (self != nil) {
        NSLog(@"ArrayClass inited");
        array = [[NSMutableArray alloc] init];
    }
    return self;
}

@end

Then I initialize an instance of this class from another class:

ArrayClass *arrayClass = [[ArrayClass alloc] init];
                [arrayClass.array addObject:image];
                NSUInteger count = [arrayClass.array count];
                NSLog(@"%@", count);

But when I try to add an object to the mutable array, the app crashes and Xcode 4.3 shows:

Removing the addObject call makes the app run fine. What am I doing wrong that would cause the app to crash?

Answer 1

This is wrong:

NSUInteger count = [arrayClass.array count];
NSLog(@"%@", count);

You want:

NSLog(@"%u", count);

%@ is used to specify that the argument is an object. However, an NSUInteger is a primitive value, not an object. You use %u for unsigned ints.