ios - 如何访问父 View Controller ？

Question

我正在使用这段代码在 ViewControllerA 中推送一个 View Controller :

DatePickerViewController *viewController = [[DatePickerViewController alloc] initWithNibName:@"DatePickerViewController" bundle:nil];
NSMutableArray *info = [[NSMutableArray alloc] initWithObjects:@"Exam Duration",nil];
[viewController setInfo:info];
[info release];
[self.navigationController pushViewController:viewController animated:YES];
[viewController release];

在滑入的DatePickerViewController 中，它有一个文本字段。在 ViewControllerA 中，一旦触发了 viewWillDisappear 方法，我如何获取此文本字段的值，这是为了保存数据。

Answer 1

有几种方法可以做到这一点。最好是使用委托(delegate)模式或通知系统。

你选择哪一个取决于你的愿望。如果您只是想让“父 Controller ”知道该值，请使用委托(delegate)方法。

使用委托(delegate)或通知创建松耦合结构并使可重用类成为可能。

编辑:一些示例代码。当心:未经测试且来 self 的脑海!

DatePickerViewController.h

@protocol DatePickerViewControllerDelegate
    -(void)datePicker:(DatePickerViewController *)picker pickedDate:(NSDate *)date;
@end

DatePickerViewController.m

- (void)viewWillDisappear:(BOOL)animated {
    [self.delegate datePicker:self pickedDate:theDate]; //Delegate is an ivar
    [super viewWillDisappear:animated];
}

ViewControllerA.m

//
DatePickerViewController *viewController = [[DatePickerViewController alloc] initWithNibName:@"DatePickerViewController" bundle:nil];
NSMutableArray *info = [[NSMutableArray alloc] initWithObjects:@"Exam Duration",nil];
[viewController setInfo:info];
[info release];
[viewController setDelegate:self]; // Set the delegate of the date picker
[self.navigationController pushViewController:viewController animated:YES];
[viewController release];
//

-(void)datePicker:(DatePickerViewController *)picker pickedDate:(NSDate *)date; {
     //Deal with the new date here
}