NSMutableArray是否正在影响另一个NSMutableArray？

Question

I have two NSMutableArray s, both getting the same data. My problem is that when I assign the same data to both the mutable arrays from different dictionaries and perform operations on one NSMutableArray , it is affecting both arrays.

When I perform operations like replaceObjectAtIndex:WithObject: , the first time, the array is not affected but when the second replace is called both arrays have the replaced value. I think it is a reference issue.

Does anyone have a solution to this?

Name of the NSMutableArrays is helper.urlsRecording and helper.holdingArr .

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
NSMutableDictionary *dict2 = [[NSMutableDictionary alloc] init];
[dict setValue:outputFileURL forKey:@"URL"];
[dict setValue:@"1" forKey:@"index"];
[dict2 setValue:outputFileURL forKey:@"URL"];
[dict2 setValue:@"1" forKey:@"index"];
[helper.urlsRecording addObject:dict];
[helper.holdingArr addObject:dict2];


[helper.urlsRecording replaceObjectAtIndex:button.tag withObject:urlAr];//When this called second time, both the arrays is effected(helper.urlsRecording as well as helper.holdingArr).

How can I prevent the copying of the reference to another array?

Button Click:

if([button isSelected] == NO){

     NSLog(@"Url Recording : %@",helper.urlsRecording);
     [[helper.urlsRecording objectAtIndex:button.tag] removeObjectForKey:@"URL"];
     button.selected = YES;
     NSLog(@"Url Recording : %@",helper.urlsRecording);
}
else{
     [helper.urlsRecording replaceObjectAtIndex:button.tag withObject:[helper.holdingArr objectAtIndex:button.tag]];
     button.selected = NO;
     NSLog(@"Url Recording : %@",helper.urlsRecording);

 }

Note: NSMutableArray is defined globally in a class to access.

Answer 1

This is because your instance values are same for both dictionary.

So First create one mutableDictionary like below

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
[dict setValue:outputFileURL forKey:@"URL"];
[dict setValue:@"1" forKey:@"index"];

And create second dictionary through mutableCopy, so instance will be different for both.

NSMutableDictionary *dict2 = [dict mutableCopy];

After that you can add them in to NSMutableArray and update accordingly.

Answer 2

Take a copy / mutableCopy dictionary & then add object to the MutableArray

[helper.urlsRecording addObject:[dict copy]];
[helper.holdingArr addObject:[dict2 copy]];