iphone - 将 uidatepicker 格式化为另一个 nsdate

Question

我有一个 UIDatePicker，我使用它获取日期:

   NSDate *pickerDate = [datePickerView date];

我想根据 pickerDate 中的星期几和时间 (HH:mm:ss) 创建一个 future 的日期。这是我正在使用的代码，但它生成的日期是错误的:

更新代码

        //format the uidatepicker
        NSDate *dateSet = pickerDate;
        NSDateFormatter *df = [[NSDateFormatter alloc] init];
        [df setTimeZone:[NSTimeZone localTimeZone]];
        [df setDateFormat:@"EEEE HH:mm:ss"];
        NSString *dateSetString = [df stringFromDate:dateSet];

        NSLog(@"repeatDateString %@",dateSetString);//prints "Tuesday 12:12:43"

        //create a new nsdate using the new format
        NSDateFormatter *dateFormat2 = [[NSDateFormatter alloc] init];
        [dateFormat2 setTimeZone:[NSTimeZone localTimeZone]];
        [dateFormat2 setDateFormat: @"EEEE HH:mm:ss"];

        NSDate *newDate = [[NSDate alloc] init];
        newDate = [dateFormat2 dateFromString:dateSetString];

        NSLog(@"new Date %@",newDate);//prints "1970-01-06 04:42:43 +0000"

Answer 1

问题是您的日期字符串不包含选择器中的所有信息，并且不包含足够的信息来重新创建日期。它缺少日、月和年，因此当您重新创建它时，它会假定您希望从 iOS 的 NSDate 日历系统的开头开始。

您要么需要存储从选择器收到的NSDate(最好)，要么需要使用包含足够信息的日期格式来创建特定的日期和时间。

编辑
根据您的评论，您只想使用 datePicker 中的工作日和时间，并使用这些值确定 future 的下一个日期。下面是实现这一点的代码:

NSCalendar          *cal            = [NSCalendar currentCalendar];

NSDate              *pickerDate     = self.datePickerView.date;
NSDateComponents    *pickerComps    = [cal components:  NSWeekdayCalendarUnit |
                                                        NSHourCalendarUnit |
                                                        NSMinuteCalendarUnit |
                                                        NSSecondCalendarUnit
                                             fromDate:pickerDate];

NSDate              *currentDate    = [NSDate date];
NSDateComponents    *currentComps   = [cal components:  NSYearCalendarUnit | 
                                                        NSMonthCalendarUnit | 
                                                        NSWeekdayCalendarUnit |
                                                        NSDayCalendarUnit |
                                                        NSHourCalendarUnit |
                                                        NSMinuteCalendarUnit |
                                                        NSSecondCalendarUnit
                                             fromDate:currentDate];

// Start with the current date and add/subtract the number of days needed to make it the same day of the week
NSDateComponents    *newComps       = [currentComps copy];
NSUInteger          weekdayDiff     = pickerComps.weekday - currentComps.weekday;
newComps.day                        = newComps.day + weekdayDiff;
// If needed, add 7 days in order to move this date into the future
if (newComps.day < currentComps.day) {
    newComps.day = newComps.day + 7;
}

NSDate *newDate = [cal dateFromComponents:newComps];
if ([newDate compare:currentDate] == NSOrderedAscending) {
    // This is true when the weekday started out the same but the time of day is earlier in the picker.  
    // Add 7 days
    newComps.day = newComps.day + 7;
    newDate = [cal dateFromComponents:newComps];
}

NSLog(@"%@", newDate);