Remove object from NSMutableArray after parsing JSON - objective-c

Question

The JSON source formatted with jsonviewer.stack.hu:
My Parse Method (simplified):
- (void)parseMethod {
// OTHER STUFF
arrayList = [[NSMutableArray alloc] init];
NSURL *url2 = // THE URL SOURCE OF JSON OBJECT, ON A REMOTE SERVER
NSURLRequest *request2 = [NSURLRequest requestWithURL:url2 cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:5.0];
AFJSONRequestOperation *operation2 = [AFJSONRequestOperation
JSONRequestOperationWithRequest:request2
success:^(NSURLRequest *request2, NSHTTPURLResponse *response2, id JSON)
{
arrayList = [JSON objectForKey:#"list"];
// HERE I TRIED TO WRITE [arrayListPrev removeObjectAtIndex:0];
NSMutableArray *arrayList1 = [arrayList valueForKey:#"list1"];
}
failure:^(NSURLRequest *request2, NSHTTPURLResponse *response2, NSError *error2, id JSON2) {
}];
[operation2 start];
}
The problem:
After the parsing I want to remove the FIRST OBJECT of array named "list", because I must populate the rows of a UITableView with all the values of list1 in the arrays EXCEPT the first ( list array->array number 0->list1 value of 0 ). I have tried the code:
[arrayList removeObjectAtIndex:0];
In several position but app crashes with error:'-[__NSCFArray removeObjectAtIndex:]: mutating method sent to immutable object'... so what's the best way to REMOVE the FIRST object (array number 0) from that NSMutableArray *list AFTER the parsing, to ELIMINATE The list1 value of 0 object? Thanks!

Answer 1

In spite of you write arrayList = [[NSMutableArray alloc] init];
Here, as i guess, you assign simple immutable array instance
arrayList = [JSON objectForKey:#"list"];
You can do this instead:
arrayList = [[JSON objectForKey:#"list"] mutableCopy];
[arrayList removeObjectAtIndex:0];

Answer 2

The problem is that you are working with an NSArray and not an NSMutableArray. This is probably due to the fact your parser returns immutable objects. What you need to do is take that NSArray, create an NSMutableArray with it and then remove the first object
NSMutableArray *_arrayList = [NSMutableArray arrayWithArray:arrayList];
[_arrayList removeObjectAtIndex:0];
// dont forget to store your array wherever you need it

Answer 3

The Error shows that your array is having value of immutable type.Use a mutable copy or initialize your arrayList with -arrayWithArray: method.Hope it fixes the problem.
Note: allocate NSMutableArray to initialize with initWithCapacity method

Answer 4

As other's have suggested, you're working with an NSArray, which is not Mutable (Editable). I'm going to add my input though with a new function:
NSMutableArray *mutableArrayList = [arrayList mutableCopy];
This creates a mutable copy of the array.