Whats is the easiest way to randomize sounds - ios

Question

I have 11 sounds for each soundpack. They are named:
testpack1.mp3,
testpack2.mp3 and so on.
My player initialises them with this code:
NSString * strName = [NSString stringWithFormat:#"testpack%ld", (long) (value+1)];
NSString * strPath = [[NSBundle mainBundle] pathForResource:strName ofType:#"mp3"];
NSURL * urlPath = [NSURL fileURLWithPath:strPath];
self.audioplayer = [[AVAudioPlayer alloc] initWithContentsOfURL:urlPath error:NULL];
This sounds will be played by pressing buttons. For example, I have generated 4 buttons, this 4 buttons play every time only testpack1-4.mp3 but I want that my player takes random out of the 11 sounds. What's the easiest solution?
Note: I don't want to repeat the mp3 unless all are played

Answer 1

How about this?
int randNum = rand() % (11 - 1) + 1;
The formuale is like below
int randNum = rand() % (maxNumber - minNumber) + minNumber;

Answer 2

A suggestion:
It declares 3 variables as static variables, played is a simple C-Array
static UInt32 numberOfSounds = 11;
static UInt32 counter = 0;
static UInt32 played[11];
The method playSound() resets the C-Array to zero values if the counter is 0 and sets the counter to the number of sounds.
When the method is called the random generator creates an index number.
If the value at that index in the array is 0 the sound is played, the index in the array is set and the counter is decreased.
If the sound at that index has been played yet, loop until a non-used index is found.
- (void)playSound
{
if (counter == 0) {
for (int i = 0; i < numberOfSounds; i++) {
played[i] = 0;
}
counter = numberOfSounds;
}
BOOL found = NO;
do {
UInt32 value = arc4random_uniform(numberOfSounds) + 1;
if (played[value - 1] != value) {
NSString * strName = [NSString stringWithFormat:#"testpack1-%d", value];
NSString * strPath = [[NSBundle mainBundle] pathForResource:strName ofType:#"mp3"];
NSURL * urlPath = [NSURL fileURLWithPath:strPath];
self.audioplayer = [[AVAudioPlayer alloc] initWithContentsOfURL:urlPath error:NULL];
played[value - 1] = value;
counter--;
found = YES;
}
} while (found == NO);
}