将字符串转换为日期（ios5）

Question

我已经尝试了一切，但无法使其正常工作。如果我将变量“dateStr”设置为@“20082233”，一切都很完美。

当我转换为日期时，它返回一个空值。即使我将dateStr设置为没有stringWithFormat的NSSTring，它仍然不起作用。日期结果返回NULL。

我做错了什么？

// If I manually set it, it works great
// NSString *dateStr = @"20081122";

// If I pull the value from the array, it does not work even if the value is exactly the same. 
NSString *dateStr = [NSString stringWithFormat:@"%@", [array1 objectForKey:@"date_string"]];


    // Convert string to date object
    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"yyyyMMdd"];
    NSDate *date = [dateFormat dateFromString:dateStr];  

    // Convert date object to desired output format
    [dateFormat setDateFormat:@"EEEE MMMM d, YYYY"];
    dateStr = [dateFormat stringFromDate:date];  



    NSLog(@"Date Conversion1: %@", date);
    NSLog(@"Date Conversion: %@", dateStr);
    NSLog(@"Original value: %@",[array1 objectForKey:@"date_string"] );

values:
2012-04-28 17:08:04.226 ModaApp2[4286:13503] Date Conversion1: (null)
2012-04-28 17:08:04.227 ModaApp2[4286:13503] Date Conversion: (null)
2012-04-28 17:08:04.228 ModaApp2[4286:13503] Original value: 20081122