Shuffle Two NSMutableArray independently - objective-c

Question

I'm creating two NSMutableArray in my viewDidLoad, I add it in a NSMutableDictionary. When I tried shuffling it with one array, It is okay. But the problem is when Im shuffling two arrays independently its not working,somehow the indexes got mixed up.
Here is my code for my array (1st Array):
self.items1 = [NSMutableArray new];
for(int i = 0; i <= 100; i++)
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:#"[Images%d.png", i]];
if([[NSFileManager defaultManager] fileExistsAtPath:savedImagePath]){
self.container = [[NSMutableDictionary alloc] init];
[container setObject:[UIImage imageWithContentsOfFile:savedImagePath] forKey:#"items1"];
[container setObject:[NSNumber numberWithInt:i] forKey:#"index1"];
[items1 addObject:container];
}
}
NSLog(#"Count : %d", [items1 count]);
[items1 enumerateObjectsUsingBlock:^(id object, NSUInteger index, BOOL *stop) {
NSLog(#"%# images at index %d", object, index);
}];
(2nd Array):
self.items2 = [NSMutableArray new];
for(int i = 0; i <= 100; i++)
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:#"secondImages%d.png", i]];
NSLog(#"savedImagePath=%#",savedImagePath);
if([[NSFileManager defaultManager] fileExistsAtPath:savedImagePath]){
self.container = [[NSMutableDictionary alloc] init];
[container setObject:[UIImage imageWithContentsOfFile:savedImagePath] forKey:#"items2"];
[container setObject:[NSNumber numberWithInt:i] forKey:#"index2"];
[items2 addObject:container];
}
}
NSLog(#"Count : %d", [items2 count]);
[items2 enumerateObjectsUsingBlock:^(id object, NSUInteger index, BOOL *stop) {
NSLog(#"%# images at index %d", object, index);
}];
My view for the iCarousel where im using my array:
- (UIView *)carousel:(iCarousel *)carousel viewForItemAtIndex:(NSUInteger)index reusingView:(UIView *)view
{
if (carousel == carousel1)
{
NSDictionary *obj = [items1 objectAtIndex:index];
view = [[UIImageView alloc] initWithImage:[obj objectForKey:#"items1"]];
view.tag = index;
}
else
{
NSDictionary *obj = [items2 objectAtIndex:index];
view = [[UIImageView alloc] initWithImage:[obj objectForKey:#"items2"]];
view.tag = index;
}
return view;
}
then my shuffle code(Which I tried duplicating for the other array,but not working also):
srandom(time(NULL));
NSUInteger count = [items1 count];
for (NSUInteger i = 0; i < count; ++i) {
int nElements = count - i;
int n = (random() % nElements) + i;
[items1 exchangeObjectAtIndex:i withObjectAtIndex:n];
}
How am I going to shuffle it using above code (or if you have other suggestions) with two arrays? Thanks
My other problem is when I tries subclassing the class for the shuffle method or either use the above code, their index mixed. For example:
Object: apple, ball, carrots, dog
Indexes: 1 2 3 4
but in my View when shuffled:
Object: carrots, apple, dog, balle
Indexes: 2 4 1 3
I also have a method, that when the carousel stop, it will delete the image on view.

Answer 1

the cleanest solution: use a Objective-C Category
NSMutableArray+RandomUtils.h
#import <Foundation/Foundation.h>
#interface NSMutableArray (RandomUtils)
-(void)shuffle;
#end
NSMutableArray+RandomUtils.m
#import "NSMutableArray+RandomUtils.h"
#implementation NSMutableArray (RandomUtils)
-(void)shuffle
{
NSUInteger count = [self count];
for (NSUInteger i = 0; i < count; ++i) {
NSUInteger nElements = count - i;
NSUInteger n = (arc4random() % nElements) + i;
[self exchangeObjectAtIndex:i withObjectAtIndex:n];
}
}
#end
import it, wherever you what to shuffle a MSMutableArray
[array1 shuffle];
[array2 shuffle];
I tried to reproduce your mixed indexes problem, but I can't
NSMutableArray *sarray = [NSMutableArray arrayWithArray: #[#"carrots", #"apple", #"dog", #"balle"]];
NSLog(#"%#", sarray);
[sa enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSLog(#"%# object at index %lu", obj, idx);
}];
[sarray shuffle];
NSLog(#"%#", sarray);
[sarray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSLog(#"%# object at index %lu", obj, idx);
}];
results in
(
carrots,
apple,
dog,
balle
)
carrots object at index 0
apple object at index 1
dog object at index 2
balle object at index 3
(
balle,
dog,
carrots,
apple
)
balle object at index 0
dog object at index 1
carrots object at index 2
apple object at index 3
BTW: your example is aslo incorrect: with four objects in an array the indices should start with 0 and maximum is 3. you have 1 and 4.
so array is shuffled and indexes are ok. You must have some other problem in code, that you didn't show.
You should give up your real code.
I am still ot sure, if I understand, what you want. But from your comments I assume, you want to shuffle an array but keep the old indices. This is just not possible, as the index is the position of an object inside an array. But you are always free to save the original index somewhere.
Or you just copy an array, shuffle one of those. Now ho can ask for the index of an object in both arrays.
NSArray *originalArray = #[#"carrots", #"apple", #"dog", #"balle"];
NSLog(#"%#", originalArray);
[originalArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSLog(#"%# object at index %lu", obj, idx);
}];
NSArray *shuffledArray = [originalArray arrayShuffled];
NSLog(#"%#", shuffledArray);
[shuffledArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSLog(#"%# object at index %lu %lu", obj, idx, [originalArray indexOfObject:obj]);
}];

Answer 2

Assuming the idea is to shuffle two array in the same order then you just need to do the exchange of the 2nd array right after the 1st array?
NSUInteger count = [items1 count];
for (NSUInteger i = 0; i < count; ++i) {
int nElements = count - i;
int n = (random() % nElements) + i;
[items1 exchangeObjectAtIndex:i withObjectAtIndex:n];
[items2 exchangeObjectAtIndex:i withObjectAtIndex:n];
}

Answer 3

Assuming that you have two different array of images which you need to shuffle the images.
for(int i = 0; i <= 100; i++)
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:#"[Images%d.png", i]];
if([[NSFileManager defaultManager] fileExistsAtPath:savedImagePath]){
//Lazy initialization of dictionary
NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
[dict setObject:[UIImage imageWithContentsOfFile:savedImagePath] forKey:#"items1"];
[dict setObject:[NSNumber numberWithInt:i] forKey:#"index1"];
[items1 addObject:dict];
[dict release];
}
}
add the object to 2nd array in the same way.
NSUInteger count = [items1 count];
for(int i = 0 ;i < count; i++)
{
int nElements = count - i;
int n = (random() % nElements) + i;
[items1 exchangeObjectAtIndex:i withObjectAtIndex:n];
}
second array shuffling
NSUInteger count = [items2 count];
for(int i = 0 ;i < count; i++)
{
int nElements = count - i;
int n = (random() % nElements) + i;
[items2 exchangeObjectAtIndex:i withObjectAtIndex:n];
}
this should work. If you still find the problem let me know.