保存UIDatePicker退出时选择的日期

Question

我试图在每次视图出现时加载用户上次选择的日期。

当我的 datePicker 更改值时，将调用此 IBAction。 datepick 是我的 datePicker

我这样做是为了保存到它的 rootVC 属性。

- (void)viewWillDisappear:(BOOL)animated {
    BookingViewController *bookingVC = [[BookingViewController alloc] init];
    bookingVC.selectedDate = [datepick date];
    [bookingVC release];
}

每次视图出现时加载它。

- (void)viewWillAppear:(BOOL)animated
{       
    // set datePicker Range.
    NSDate *todaysDate = [NSDate date];
    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents *dateComponents = [[NSDateComponents alloc] init];
    [dateComponents setHour:48];
    NSDateComponents *dateComponents2 = [[NSDateComponents alloc] init];
    [dateComponents2 setMinute:30];
    NSDate *maxDate = [gregorian dateByAddingComponents:dateComponents toDate:todaysDate  options:0];
    NSDate *minDate = [gregorian dateByAddingComponents:dateComponents2 toDate:todaysDate  options:0];
    datepick.maximumDate = maxDate;
    datepick.minimumDate = minDate;
    if (self.dateToSet == nil) {
        [datepick setDate:minDate animated:YES];
    }
    else {
        [datepick setDate:dateToSet animated:YES];
    }
    [dateComponents release];
    [dateComponents2 release];
    [gregorian release];
    choice = [datepick date];   
    choiceString = [dateFormatter stringFromDate:choice];
    dateTextfield.text = choiceString;

}

在推送 dateViewController 之前，我将保存的日期（self.selectedDate）传递给 dateViewController.dateToSet 属性，

- (void)advanceBooking:(id) sender {
    DateViewController *dateViewController= [[DateViewController alloc]
                                           initWithNibName:@"DateViewController" 
                                           bundle:nil];
    if (self.selectedDate == nil) {
        selectedDate = [[NSDate alloc] init];
    }
    dateViewController.dateToSet = self.selectedDate;
    NSLog(@"dateVC.dateToSet :%@ selectedDate:%@", dateViewController.dateToSet, self.selectedDate); // both read as current date though it was the first call? weird.
    dateViewController.hidesBottomBarWhenPushed = YES;
    dateViewController.navigationItem.hidesBackButton = YES;
    [self.navigationController pushViewController:dateViewController animated:YES];
    [dateViewController release];

}

我想它与我初始化属性的方式有关？我应该什么时候初始化它们？

Answer 1

尝试在创建时设置 datePicker 的 parentViewController：

dateViewController.parentViewController = self;

并在方法 viewWillDisappear 中执行以下操作：

((BookingViewController *)self.parentViewController).selectedDate = [datepick date];

在 BookingViewController 中，您应该声明并综合属性NSDate *selectedData。

但为此目的更正确的是使用协议+委托方法。

Answer 2

每次加载视图 (viewDidLoad) 时，都会将该值重新设置为“now”。在 viewDidLoad 中，您不应初始化 choice。

Answer 3

由于我正在向上传递层次结构，因此我不应该创建该类的新对象。

因此，我应该取回已经创建的对象，

在 DateViewController.m（子视图）

NSArray *viewControllers = [self.navigationController viewControllers];
BookingViewController *bookingVC = (BookingViewController *)[viewControllers objectAtIndex:viewControllers.count - 2];
[bookingVC setSelectedDate:[datepick date]];

在 BookingViewController.m（父视图）

if (self.selectedDate != nil) {
    dateViewController.dateToSet = self.selectedDate;
}

然后每次在 DateViewController.m 的 viewDidLoad 期间设置它

if (self.dateToSet == nil) {
    [datepick setDate:minDate animated:YES];
}
else {
    [datepick setDate:dateToSet animated:YES];
}