Deep copy of an NSMutableArray of custom objects with NSMutableArray members

Question

I'm trying to make a deep copy of an NSMutableArray whose objects are instances of a custom class similar to this:

@interface CustomParent : NSObject
@property NSInteger Id;
@property (strong, nonatomic) NSString *IdStr;
@property (weak, nonatomic) NSDate *Date; 
@property (strong, nonatomic) NSMutableArray *CustomChildren;
@property (strong, nonatomic) CustomType *Type;
@property float Value;
@end

I know there are lots of posts dealing with copying objects, but I don´t find examples for getting a complete copy of objects with collection members or properties. NSMutableArray *dstArray = [[NSMutableArray alloc] initWithArray:srcArray copyItems:YES]; raises an exception involving the copyWithZone method.

How can I do this? Thanks!

take a look at the NSCoding protocol : developer.apple.com/library/mac/#documentation/cocoa/reference/… — Lescai Ionel
– Lescai Ionel, Commented Jun 27, 2013 at 13:34
@GabrielePetronella I read the post you referred and it seems to work, thanks! — AppsDev
– AppsDev, Commented Jun 28, 2013 at 17:55
@LescaiIonel I tried NSCoding before and it takes a lot of time for copying many objects connected to a class. Thins NSCopying should be faster. — Alex Cio
– Alex Cio, Commented Feb 17, 2015 at 15:01

Community · Accepted Answer · 2017-05-23 12:17:08Z

13

In order to deep copy the content of the array

[[NSMutableArray alloc] initWithArray:srcArray copyItems:YES];

will send copyWithZone: to every object inside the collection. If they don't respond to this selector, you'll get a crash.

Have your CustomParent class to conform to the NSCopying protocol and you're done.

Here's some extra info on how do achieve it: Implementing NSCopying

edited May 23, 2017 at 12:17

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answered Jun 27, 2013 at 13:35

Gabriele Petronella

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