Question

i have two nsmutablearray:

@property (nonatomic, strong) NSMutableArray *calSeries;
@property (nonatomic, strong) NSMutableArray *calSeries2Copy;

then i do this:

self.calSeries = [self getSeries];
self.calSeries2Copy = [NSMutableArray arrayWithArray:self.calSeries];

the getSeries method fetchObject from the core data, but if i change an element in the calSeries, it change also in the calSeries2Copy, how i can create two array separately so as when i change an element in one array don’t change also in the other array?

Answer 1

Try this,

self.calSeries2Copy = [[NSMutableArray alloc] initWithArray:self.calSeries copyItems:YES];

As per documentation, this should copy if you have implemented NSCopying protocol.

flag

If YES, each object in array receives a copyWithZone: message to
create a copy of the object—objects must conform to the NSCopying
protocol. In a managed memory environment, this is instead of the
retain message the object would otherwise receive. The object copy is
then added to the returned array.

If NO, then in a managed memory environment each object in array
simply receives a retain message when it is added to the returned
array.

Discussion

After an immutable array has been initialized in this way,
it cannot be modified.

The copyWithZone: method performs a shallow copy. If you have a
collection of arbitrary depth, passing YES for the flag parameter will
perform an immutable copy of the first level below the surface. If you
pass NO the mutability of the first level is unaffected. In either
case, the mutability of all deeper levels is unaffected.