Printing from NSMutableArray - ios

Question

So i want to print the users in an NSMutableArray. But the strings keep coming out as nil.
here is what i have:
int users = 0;
- (IBAction)addNewUser:(id)sender {
NSString *string;
string = userNameTextField.text;
[usernameArray insertObject:string atIndex:users];
users++;
[self showUsers];
}
-(void)showUsers{
for (int i = 0; i < users; i++){
NSString *s = textView.text;
NSString *add;
add = [NSString stringWithFormat:#"%# ",[usernameArray objectAtIndex:i]];
NSString *display = [NSString stringWithFormat:#"%# \n %#", s, add];
textView.text = display;
}
}
i have also tried
-(void)showUsers{
for (int i = 1; i < users; i++){
NSString *s = textView.text;
NSString *add;
add = [usernameArray objectAtIndex:i];
NSString *display = [NSString stringWithFormat:#"%# \n %#", s, add];
textView.text = display;
}
}

Answer 1

First of all try using more comprehensive names for the objects. I'm rewriting your code.
Common Causes for the problem : Array not initialized, you are starting your for cycle with int i equal to 1, so you are missing the object at index 0 at your mutable array. Try the following code.
#interface InterfaceName : InterfaceInherits <IfDelegate> {
int usersCount;
NSMutableArray * usernameArray;
}
#implementation InterfaceName
/*There's no more confident way to initialize a variable than in the init method of the class. */
-(id)init{
usersCount = 0;
//You have to be sure that your array is not nil
usernameArray = [NSMutableArray alloc]init]];
return self;
}
- (IBAction)addNewUser:(id)sender {
NSString *username = [usernameTextField text];
[usernameArray insertObject:username atIndex:usersCount];
usersCount++;
//I'll omit the display as I'm not sure what you were doing with it.
}
-(void)showUsers{
for (int i = 0; i < usersCount; i++){
NSString *retrievedUser = [usernameArray objectAtIndex:i];
NSString *display = [NSString stringWithFormat:#"User Retrieved : %#",retrievedUser];
textView.text = display;
}
}
#end