ios - -[NSDateFormatter dateFromString :] returns nil

Question

    NSString *lower = [NSString stringWithFormat:@"%@",[newDates objectAtIndex:0]];
    NSString *higher = [NSString stringWithFormat:@"%@",[newDates objectAtIndex:[newDates count]-1]];
    NSLog(@"%@",lower);
    NSLog(@"%@",higher);

    NSDateFormatter *df = [[NSDateFormatter alloc] init];
    [df setDateFormat:@"yyyy-MM-dd"];
    NSDate *dtLower = [df dateFromString:lower];

    NSDate *dtHigher = [df dateFromString:higher];
    [df release];
    NSDateFormatter *df1 = [[NSDateFormatter alloc] init];
    [df1 setDateFormat:@"yyyy-MM-dd"];
    NSString * lowerDate = [df1 stringFromDate:dtLower];
    NSString * higherDate = [df1 stringFromDate:dtHigher];
    UILabel *dateLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 31, self.view.frame.size.width, 30)];
    [dateLabel setTextColor:[UIColor grayColor]];
    dateLabel.text = [NSString stringWithFormat:@"%@ - %@",lowerDate,higherDate];
    [self.view addSubview:dateLabel];

控制台中 lower 和 higher 的输出是:

2011-05-23 14:55:52.767 Vocab[4225:207] 2011-05-23 03:58:22
2011-05-23 14:55:53.781 Vocab[4225:207] 2011-05-23 07:14:56

这里上面的代码对我不起作用。 higher 和 lower 的值不为空，但当我尝试使用 NSDateFormatter 将其转换为 NSDate 时，它​​返回 nil。

所以 dtLower 和 dtHigher 返回 nil

有什么问题吗？

Answer 1

尝试设置 [df setDateFormat:@"yyyy-MM-dd HH:mm:ss"];