Question

I’m new to Objective-C and I’m trying to create a simple dictionary style app for personal use. Right now I’m attempting to make a loop that prints randomly selected NSArrays that have been added to an NSDictionary. I’d like to print each array only once. Here is the code I’m working with:

NSArray *catList = [NSArray arrayWithObjects:@"Lion", @"Snow Leopard", @"Cheetah", nil];
NSArray *dogList = [NSArray arrayWithObjects:@"Dachshund", @"Pitt Bull", @"Pug", nil]; 
...
NSMutableDictionary *wordDictionary = [[NSMutableDictionary alloc] init];
[wordDictionary setObject: catList forKey:@"Cats"];
[wordDictionary setObject: dogList forKey:@"Dogs"]; 
...
NSInteger keyCount = [[wordDictionary allKeys] count];
NSInteger randomKeyIndex = arc4random() % keyCount;

int i = keyCount;

for (i=i; i>0; i--) {
    NSString *randomKey = [[wordDictionary allKeys] objectAtIndex:randomKeyIndex];
    NSMutableArray *randomlySelectedArray = [wordDictionary objectForKey:randomKey];
    NSLog(@"%@", randomlySelectedArray);
}

This code prints the same array “i” times. Any pointers on how to exclude previously printed arrays from being printed again?

I’m wondering if removeObjectForKey: could be of any use.

Answer 1

You just need to re-calculate the random key index every time you go through the loop, and then, as you suggest, use removeObjectForKey:.

Something like this:

NSArray *catList = [NSArray arrayWithObjects:@"Lion", @"Snow Leopard", @"Cheetah", nil];
NSArray *dogList = [NSArray arrayWithObjects:@"Dachshund", @"Pitt Bull", @"Pug", nil]; 

//...

NSMutableDictionary *wordDictionary = [[NSMutableDictionary alloc] init];
[wordDictionary setObject: catList forKey:@"Cats"];
[wordDictionary setObject: dogList forKey:@"Dogs"]; 

//...

while ([wordDictionary count] > 0) {    
    NSInteger keyCount = [wordDictionary count];
    NSInteger randomKeyIndex = arc4random() % keyCount;
    NSString *randomKey = [[wordDictionary allKeys] objectAtIndex:randomKeyIndex];
    NSMutableArray *randomlySelectedArray = [wordDictionary objectForKey:randomKey];
    NSLog(@"%@", randomlySelectedArray);

    [wordDictionary removeObjectForKey: randomKey];
}