NSDateFormatter return null - iphone

Question

I'm trying to format a NSDate to a string with date format of yyyyMMdd, here's the code
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"yyyyMMdd"];
NSDate *date =data.createdTime;
NSLog(#"%#",date);
NSLog(#"%#",[dateFormatter stringFromDate:date]);
the NSLog return me this value
Tue, 24 May 2011 0:05:01 +0800
(null)
Anyone know which part is wrong?
Thanx in advance.

Answer 1

Perhaps currentArticle.createdTime is a valid date but data.createdTime is nil? In addition, you are performing the -setDateFormat: selector on dateFormat, but it seems like your date formatter is dateFormatter.
Try the following code:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat: #"yyyyMMdd"];
NSDate *date = data.createdTime;
NSLog(#" Normal Date = %#", date);
NSLog(#"Formatted Date = %#", [dateFormatter stringFromDate: date]);
[dateFormatter release];
If date is nil, then both NSLog() calls will tell you.
Edit
Double check that data.createdTime is an NSDate instance. Perhaps it is an instance of another class, such as NSString, whose -description returns the displayed date. This would explain why NSLog() “shows” the date, but the formatter is returning nil.
BOOL isDate = [data.createdTime isKindOfClass: [NSDate class]];
NSLog(#"Date %# a date.", isDate ? #"is" : #"is not");

Answer 2

[dateFormat setDateFormat:#"yyyyMMdd"];
Should be:
[dateFormatter setDateFormat:#"yyyyMMdd"];
If it still isn't working then something is wrong with data.createdTime; because I ran this code and recieved the expected output:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyyMMdd"];
NSDate *date = [NSDate date];
NSLog(#"%#",date);
NSLog(#"%#",[dateFormatter stringFromDate:date]);