mutating method sent to immutable object

Question

When I use this method first time it works fine, but when I called it second time I get the error \"mutating method sent to immutable object\". The problem is at line with \"add

Answer 1

This should work:

-(IBAction) save: (id) sender {

NSMutableArray *placesT= [[NSMutableArray alloc]initWithArray:[[NSUserDefaults standardUserDefaults]

objectForKey:@"placesT"]];

if (!placesT) {
    placesT=[[[NSMutableArray alloc] init] autorelease];
}

[placesT addObject: [NSString stringWithFormat:@"%@", tagF.text] ];

NSUserDefaults *tUD=[NSUserDefaults standardUserDefaults];
[tUD setObject:placesT forKey:@"placesT"];
[tUD synchronize];

[self dismissModalViewControllerAnimated:YES]; }