NSString和NSDate相互转化

//目标格式：yyyy-MM-dd
NSString *dateStr = @"2015-9-15";
NSLog(@"initial dateStr:%@",dateStr);
NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
[inputFormatter setDateFormat:@"yyyy-MM-dd"];
NSDate* inputDate = [inputFormatter dateFromString:dateStr];
NSLog(@"inputDate:%@",inputDate);
NSDateFormatter* outputFormatter = [[NSDateFormatter alloc] init];
[outputFormatter setDateFormat:@"yyyy-MM-dd"];
NSString *targetDateStr = [outputFormatter stringFromDate:inputDate];
NSLog(@"targetDateStr:%@",targetDateStr);