deep copy NSMutableArray in Objective-C ?

Question

Hi All,

Is there any built-in function in Objective-C allows me to deep copy a NSMutableArray?

I looked around, some people say [aMutableArray copyWithZone:nil] works as deep copy. But I tried it seems no.

Right now I am manually doing the copy one by one (a 9*9 array):

//deep copy a 9*9 mutable array to a passed-in reference array

-deepMuCopy : (NSMutableArray*) array 
    toNewArray : (NSMutableArray*) arrayNew {

    [arrayNew removeAllObjects];//ensure it's clean

    for (int y = 0; y<9; y++) {
     [arrayNew addObject:[NSMutableArray new]];
     for (int x = 0; x<9; x++) {
      [[arrayNew objectAtIndex:y] addObject:[NSMutableArray new]];

      NSMutableArray *aDomain = [[array objectAtIndex:y] objectAtIndex:x];
      for (int i = 0; i<[aDomain count]; i++) {

       //copy object by object
       NSNumber* n = [NSNumber numberWithInt:[[aDomain objectAtIndex:i] intValue]];
       [[[arrayNew objectAtIndex:y] objectAtIndex:x] addObject:n];
      }
     }
    }
}

Thank you.

Answer 1

It's a little bit of a hack, but the only way I know to easily do this is to archive and then immediately unarchive your array.

The catch is that your object must support the NSCoding interface, since this will be used to store/load the data.

NSArray* arrayCopy = [NSUnarchiver unarchiveObjectWithData: [NSArchiver archivedDataWithRootObject: oldArray]];

Answer 2

Doesn't it work if you simply use the initWithArray:copyItems: on NSMutableArray.

NSMutableArray *newArray = [[NSMutableArray alloc] initWithArray:oldArray copyItems:YES];

That's what they recommend here and what I remember I'm doing in my projects generally: http://lists.apple.com/archives/cocoa-dev/2008/May/msg00172.html