Question

I am storing some data (some floats, some strings) to a plist and then reading them back. When I read them back, I assign them to some ivars in my view controller. They are just ivars, not properties.

The floats take their values fine and I can NSLog them and see that they are correct. But no matter what I try, I can’t get my NSString ivars to take the string values.

Example: array positions 6 and 7 have the strings Portland, OR" and "Pacific Daylight Time" stored in them – read back from the plist into *array.

This:

cityName = [NSString stringWithFormat:@"", [array objectAtIndex:6]];
timeZoneName = [NSString stringWithFormat:@"", [array objectAtIndex:7]];
NSLog(@" >cityName from array = %@, and now the iVar is = %@", [array objectAtIndex:6], cityName);
NSLog(@" >timeZoneName from array = %@, and now the iVar is = %@", [array objectAtIndex:7], timeZoneName);

Results in this:

>cityName from array = Portland, OR, and now the iVar is = 
>timeZoneName from array = Pacific Daylight Time, and now the iVar is = 

I put a breakpoint at the end of the method where this happens and for both NSString ivars, the little pop up message says, Invalid Summary.

Answer 1

cityName = [NSString stringWithFormat:@"%@", [array objectAtIndex:6]];

The mistake is that you’ve missed the format specifier. Specifically though, if the objects in the array are already strings, you can just assign them straight to the ivar:

cityName = [array objectAtIndex:6];

Be careful about object ownership though. You don’t own the object returned by objectAtIndex: so if you need to use this ivar in many different methods, obtain ownership by sending retain, and relinquish ownership using release. Alternatively if you choose to establish cityName as a retaining or copying property of your class, use the dot-notation or accessor method:

self.cityName = [array objectAtIndex:6];

// or

[self setCityName:[array objectAtIndex:6]];