Question

I have a singleton class. In this class, i am holding an array of songs. This array should not change! in my app when i choose a song from my song list, the current song is inserted to another variable. This var is Song type ( the array is array of songs ). so when i am writing

_myDataMgr._currSong = [_myDataMgr.songArray objectAtIndex:index];

Every time i will change this currSong Variable the songArray will change because currSong is point to this array. so my question is how i can create a copy of this currSong? i know somthing about NSCopy but i dont know how to use it really. thank you all.
P.S: _myDataMgr is the singleton

Answer 1

You should make your class conform to the NSCopying protocol.

@interface Song : NSObject <NSCopying>

Then, implement the method copyWithZone:

- (id)copyWithZone:(NSZone *)zone
{
    id copy = [[[self class] alloc] init];

    if (copy) {
        // Copy properties here...
    }

    return copy;
}

When you need a copy of your instance, just call copy. (I recommend to call this when you’re inserting the songs into the array in the singleton class.)

[myArray insertObject:[song copy]];