Question

All,

I have strings stored in a NSMutableArray. When a certain condition is met elsewhere in the code, the object that is FIRST in the NSMutableArray (read, objectAtIndex:0) gets removed. After it is removed, I need to shift everything down an index. Here is my example:

/*
    Index/Value
    0 - one
    1 - two
    2 - three
    3 - four
    4 - five
    5 - six
    6 - seven
*/
//removes object...
[mArray removeObjectAtIndex:0];
//I am missing something here...


//I want the value of the array to be as follows:
/*
    Index/Value
    0 - two
    1 - three
    2 - four
    3 - five
    4 - six
    5 - seven
*/

What am I missing?

EDIT: The NSMutableArray is stored in NSUserDefaults. Is that what may be causing this not to work?

EDIT2: Because it is stored in NSUserDefaults, it changes to immutable. Check out the accepted answer for the correct way to do it. Details here: crashes my app [NSMutableArray1 removeAllObjects] iphone sdk

Answer 1

If I understand your issue correctly you are storing an NSMutableArray to NSUserDefaults and then when you load it out of NSUserDefaults it throws an error when you try to mutate?

This is because when you retrieve the array from NSUserDefaults it will be an instance NSArray not NSMutableArray therefore you need to make a an instance of NSMutableArray to work with.

NSMutableArray *mArray = [[NSMutableArray alloc] initWithArray:myArrayFromNSUserDefaults];