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Changing between tabs using a Singleton class causes SIGABRT
@interface SingletonClass : NSObject
{
}

@property(nonatomic, retain) NSMutableArray *categoryArray;

+ (SingletonClass *)sharedInstance;
- (id) init;
- (void)setCategory: (NSMutableArray *) x;
- (NSMutableArray *)getCategory;

@end

#import "SingletonClass.h"

@implementation SingletonClass
@synthesize categoryArray;


static SingletonClass *sharedInstance = nil;

+ (SingletonClass *)sharedInstance {
    if (sharedInstance == nil) {
        sharedInstance = [[super allocWithZone:NULL] init];
    }
    return sharedInstance;
}

- (id)init
{
    self = [super init];

    if (self) {
        categoryArray = [[NSMutableArray alloc] init];
    }

    return self;
}

+ (id)allocWithZone:(NSZone*)zone {
    return [self sharedInstance];
}

- (id)copyWithZone:(NSZone *)zone {
    return self;
}

- (void)setCategory: (NSMutableArray *)category_array{
    categoryArray = category_array;
}

- (NSMutableArray *)getCategory{
    return categoryArray;
}

@end

SingletonClass* myapp = [SingletonClass sharedInstance];
categories = [myapp getCategory];