Question

I have a simple method in my code which looks like the following:

- (BOOL)isFirstTimeLogin  {     NSString *t_gName =      [NSString stringWithFormat:@'%@', [[NSUserDefaults standardUserDefaults] objectForKey:kGroupIdentifierKey]];     if ([t_gName isEqualToString:@''] || t_gName == nil) {         DLog(@'LoginViewController, m:::isFirstTimeLogin, First time login happening.');         return YES;     }      DLog(@'LoginViewController, m:::isFirstTimeLogin, Not a first time login.');     return NO; } 

Simply what this does is go to the Settings bundle, and retrieve a value from a PSTextFieldSpecifier. If I manually go in and add some arbitrary text, the code works as expected. However, whenever I first install the app on a new device, the first condition is executing as false, which it should be true. After stepping through the code, gdb proves that the object is indeed nil as well:

(gdb) po t_gName
(null)

What am I possibly doing wrong here? Why is it the condition is failing for the first time the app is installed and t_gName is an empty/null PSTextFieldSpecifier. I even went as far as trying to add a DefaultValue in my Settings bundle of an empty string.

Answer 1

[NSString stringWithFormat:@'%@', nil]; 

This creates something like this:

@'(null)' 

and is therefore neither nil nor equal to @''.

by the way

1. You don’t need stringWithFormat: at all.
2. Don’t check for string == nil but for !string
3. You don’t have to check for an empty string, as there is one set or it’s nil.
4. Use a better name than t_gName, there’s no reason for short names.

Like this:

- (BOOL)isFirstTimeLogin  {     NSString *groupIdentifier = [[NSUserDefaults standardUserDefaults]                                     objectForKey:kGroupIdentifierKey];     if (!groupIdentifier) {         DLog(@'First time login.');         return YES;     }      DLog(@'Not a first time login.');     return NO; }