Is there any built-in function that allows me to deep copy an NSMutableArray
?
I looked around, some people say [aMutableArray copyWithZone:nil]
works as deep copy. But I tried and it seems to be a shallow copy.
Right now I am manually doing the copy with a for
loop:
//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];
}
}
}
}
but I'd like a cleaner, more succinct solution.
As the Apple documentation about deep copies explicitly states:
If you only need a one-level-deep copy:
NSMutableArray *newArray = [[NSMutableArray alloc] initWithArray:oldArray copyItems:YES];
The above code creates a new array whose members are shallow copies of the members of the old array.
Note that if you need to deeply copy an entire nested data structure — what the linked Apple docs call a true deep copy — then this approach will not suffice. Please see the other answers here for that.