copy NSUserDefaults array and edit the array - ios

Question

I am getting crash when i am replacing the value in NSMutableArray and the message is
"Terminating app due to uncaught exception
'NSInternalInconsistencyException', reason: '-[__NSCFDictionary
setObject:forKey:]: mutating method sent to immutable object'"
What I am doing is first store an array in NSUserDefaults and then get the array . After that i am editing the copy of that array .
NSMutableArray *getArr = [[NSUserDefaults standardUserDefaults] valueForKey:#"List"];
NSMutableArray *newArray = [[NSMutableArray alloc]initWithArray:getArr copyItems:YES];
And Now I am replacing the value of new Array at particular index
for(int i = 0;i<newArray.count;i++)
{
NSDictionary *dict = [newArray objectAtIndex:i];
dict["key"] = "NewValue"
[newArray replaceObjectAtIndex:i withObject:d];
}

Answer 1

The problem is that the stored dictionary object is immutable , so you need to init a mutable one with it's content , do the job then save it again see this example
NSMutableArray*old= [NSMutableArray new];
[old addObject:#{#"key":#"value"}];
[[NSUserDefaults standardUserDefaults] setObject:old forKey:#"www"];
NSMutableArray*edited = [[[NSUserDefaults standardUserDefaults] objectForKey:#"www"] mutableCopy];
NSMutableDictionary*dic = [[NSMutableDictionary alloc] initWithDictionary:[edited objectAtIndex:0]];
dic[#"key"] = #"value2";
[edited replaceObjectAtIndex:0 withObject:dic];
[[NSUserDefaults standardUserDefaults] setObject:edited forKey:#"www"];
NSMutableArray*vvv = [[NSUserDefaults standardUserDefaults] objectForKey:#"www"];
NSLog(#"%#",vvv); /// key:value2

Answer 2

The problem is that you have only array copied as mutable. But dictionaries inside are still immutable objects. You can try making a deep mutable copy but for your case you can just do the following
for(int i = 0;i<newArray.count;i++)
{
//Just copy the dict as mutable and then change the value
NSDictionary *dict = [[newArray objectAtIndex:i] mutableCopy];
dict["key"] = "NewValue"
[newArray replaceObjectAtIndex:i withObject:dict];
}