Question

I found this post: What's the Best Way to Shuffle an NSMutableArray?

And as i try to deploy this in my own code, I cant get it working…

Can anyone help me to resolve this code?

To me it looks like the shuffle function is not called..?

here is my code:

// // shuffle2ViewController.h // shuffle2

#import

@interface shuffle2ViewController : UIViewController {
NSMutableArray *puzzles; 
int *randomSort;
}

- (void)shuffle;
@end

//=============================

// shuffle2ViewController.m

´#import "shuffle2ViewController.h"

@implementation shuffle2ViewController

(void)viewDidLoad { 
[super viewDidLoad];

NSMutableArray *puzzles = [NSMutableArray arrayWithObjects:@"1",@"2",@"3", @"4",@"5",@"6",@"7",@"8",@"9", @"10",@"11",@"12", nil];

// Call the shuffle function
[self shuffle];

// print to log

int i;

NSLog(@"NEW OLD");

NSLog(@"=================");

for (i = 0; i < 12; ++i) NSLog(@" %2i %@", i + 1, [puzzles objectAtIndex:i]); }

int randomSort(id obj1, id obj2, void *context ) {
// returns random number -1 0 1
return (random()%3 - 1); }

(void)shuffle { // call custom sort function

[puzzles sortUsingFunction:randomSort context:nil]; 
}

Giving this result:

NEW OLD
=================
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 10
11 11
12 12

Answer 1

Your problem is that you’re redeclaring the puzzles array. It’s an ivar on the class, but since you’ve got the NSMutableArray * puzzles = ... in your viewDidLoad method, it’s overriding the instance variable. If you were to NSLog(@"%@", puzzles); in your shuffle method, you’ll see that it logs (null).

The simple fix is to delete the NSMutableArray * in your viewDidLoad method.

EDIT

Also (as Peter mentions in the comments) don’t forget to retain the array.