CODEWITHSUNDEEP
xcoderandomnsmutableset
user1467534
user1467534

Reputation: 71

Can't clear/reset NSMutableSet?

This is what I'm trying to do. Get 7 random, non-repeating numbers each time my viewDidLoad starts. I got it to create the randoms, but I've been trying to clear the NSMutableSet when it loads to get a fresh set and I'm having trouble. The NSLog is clearly showing nothing is in the NSMutableSet, but it always comes up with the same numbers in the same order?

// Create set
NSMutableSet *mySet = [NSMutableSet setWithCapacity:6];

// Clear set
NSMutableSet *mutableSet = [NSMutableSet setWithSet:mySet];
[mutableSet removeAllObjects];
mySet = mutableSet;

NSLog(@"mutableSet: %@", mutableSet);  // Shows nothing
NSLog(@"mySet: %@", mySet);  // Shows nothing

// Assign random numbers to the set
while([mySet count]<=6){
    int Randnum = arc4random() % 7+1;
    [mySet addObject:[NSNumber numberWithInt:Randnum]];
}

NSLog(@"mySet1: %@", mySet);  // Always shows 5,1,6,2,7,3,4 ???

Upvotes: 1

Views: 338

Answers (1)

Martin R
Martin R

Reputation: 539815

An NS(Mutable)Set is an unordered collection, it does not preserve the order of the elements as they were inserted. So your output only shows that the set contains the numbers from 1 to 7.

You have different options to get your expected output.

  1. Use an NSMutableOrderedSet instead.

  2. Use a set to keep track of the numbers that already occurred, but store the numbers also in an array:

    NSMutableArray *numbers = [NSMutableArray array];
NSMutableSet *mySet = [NSMutableSet set];
while ([numbers count] < 6) {
    NSNumber *randNum = @(arc4random_uniform(7) + 1);
    if (![mySet containsObject:randNum]) {
        [numbers addObject:randNum];
        [mySet addObject:randNum];
    }
}
NSLog(@"numbers: %@", numbers);

  3. For a small set (like 7 numbers in your case), you could simply use an array only:

    NSMutableArray *numbers = [NSMutableArray array];
while ([numbers count] < 6) {
    NSNumber *randNum = @(arc4random_uniform(7) + 1);
    if (![numbers containsObject:randNum]) {
        [numbers addObject:randNum];
    }
}
NSLog(@"numbers: %@", numbers);

Upvotes: 1

Related Questions