Trying to access data from an array and print it out - objective-c

Question

I have made an array which I store 5 strings and 1 int into which I then store in to another array.
I'm trying to access and print out an array but it only give me this:
2016-01-11 18:47:55.429 quizgame-chrjo564[3378:145727] (null)
I've tried these alternatives:
NSLog(#"%#", [dataArray objectAtIndex:0]);
NSLog(#"%#", dataArray[0]);
Here is all my code:
#import "ViewController.h"
#interface ViewController ()
{
NSMutableArray *_questions;
}
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[self quizStart];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)prepQuestions {
[self question:#"Vad heter jag?" answer1:#"Anton" answer2:#"Christian" answer3:#"Christoffer" answer4:#"Simon" correctAnswer:2];
}
- (void)question:(NSString *)q answer1:(NSString *)a1 answer2:(NSString *)a2 answer3:(NSString *)a3 answer4:(NSString *)a4 correctAnswer:(NSInteger)c {
NSArray *tmpArray = [NSArray arrayWithObjects:
[NSString stringWithString:q],
[NSString stringWithString:a1],
[NSString stringWithString:a2],
[NSString stringWithString:a3],
[NSString stringWithString:a4],
[NSNumber numberWithInteger:c],nil];
NSLog(#"%#", q);
[_questions addObject:tmpArray];
}
- (void)quizStart {
[self prepQuestions];
NSArray *dataArray = [_questions objectAtIndex:0];
NSLog(#"%#", [dataArray objectAtIndex:0]);
}
#end
Thanks in advance
*Updated with error after change:
2016-01-11 19:28:00.816 quizgame-chrjo564[3901:202243] - [__NSCFConstantString objectAtIndex:]: unrecognized selector sent to instance 0x75030
2016-01-11 19:28:00.822 quizgame-chrjo564[3901:202243] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '- [__NSCFConstantString objectAtIndex:]: unrecognized selector sent to instance 0x75030'

Answer 1

You never initialize _questions.
Change this:
[_questions addObject:tmpArray];
to:
if (!_questions) {
_questions = [NSMutableArray array];
}
[_questions addObject:tmpArray];
Also, here's a suggestion to make your code cleaner and easier to read.
Don't needlessly use stringWithFormat:.
Use modern syntax for arrays and dictionaries.
Use modern syntax for number boxing.
In other words, you question:... method can be written as:
- (void)question:(NSString *)q answer1:(NSString *)a1 answer2:(NSString *)a2 answer3:(NSString *)a3 answer4:(NSString *)a4 correctAnswer:(NSInteger)c {
NSArray *tmpArray = #[ q, a1, a2, a3, a4, #(c) ];
NSLog(#"%#", q);
if (!_questions) {
_questions = [NSMutableArray array];
}
[_questions addObject:tmpArray];
}