Re: *** -[NSCFDictionary setObject:forKey:]: mutating method sent to immutable object

FROM : Bill Bumgarner
DATE : Tue Feb 19 20:46:39 2008

On Feb 19, 2008, at 11:24 AM, Hamish Allan wrote:
> On Feb 19, 2008 6:00 PM, Daniel Child <<email_removed>> wrote:

>> - (id) init
>> {
>>        data = [[NSMutableDictionary alloc] init];
>>        return self = [super initWithWindowNibName: @"Step1Window"];
>> }

> Always call [super init...] at the start of your init method.
> Otherwise, your superclass could be overwriting the ivar called "data"
> with, e.g., an immutable NSDictionary.


Hamish is correct in that this should be structured something like:

- init
{
   if (self = [super initWithWindowNibName: @"Step1Window"]) {
       data = [[NSMutableDictionary alloc] init];
   }
   return self;
}

Given that you declared the instance variable in the class w/the init, 
super better not be replacing your ivar!

So, how could data become a non-mutable object?

(1) Unarchival generally produces immutable objects unless you 
explicitly ask for mutable objects.

(2) You released data and replaced it with a reference to an immutable 
object

(3) You have a memory munching bug

b.bum