无法将值传回parentViewController

Question

我有masterViewController和detailViewController。Masterview推送detailView。当返回到masteViewController时，我想更新foo值。但是我只能从nslog中得到NULL。在返回导航时，如何将parenteViewContrller.foo值设置为@"bar“？

masterViewController.h

    NSString *foo; 
    -(void)setFoo:(NSString *)fooValue
    @property(nonatomic, retain) NSString *foo; 

masterViewController.m

@synthesize foo;

-(void)setFoo:(NSString *)fooValue{

    NSLog(@"updated foo:%@", fooValue);
}

detailViewController.m

-(void)goBack{
    [self.navigationController.parentViewController setValue:@"bar" forKey:@"foo"];
    [self.navigationController popViewControllerAnimated:YES];
}

Answer 1

从iOS 5开始，[UIViewController parentViewController]将不会返回您所期望的内容，相反，您应该使用[UIViewController presentingViewController]

如果你只是针对iOS 5，开始使用presentingViewController很容易，但如果不是这样，我建议你手动传递你的UIViewController：

// DetailViewController.h

@class MasterViewController;

@interface DetailViewController : UIViewController

@property (assign, nonatomic) MasterViewController *masterViewController;

@end


// DetailViewController.m

#import "DetailViewController.h"
#import "MasterViewController.h"

@implementation DetailViewController

- (void)goBack {

    [self.masterViewController setFoo:@"bar"];

    // dismiss this view controller
}

@end


// MasterViewController.h

@interface MasterViewController : UIViewController

- (void)setFoo:(NSString *)bar;

@end


// MasterViewController.m

#import "MasterViewController.h"
#import "DetailViewController.h"

@implementation MasterViewController

- (void)goForward {

    DetailViewController *detailViewController = ...;
    [detailViewController setMasterViewController:self];

    // present this view controller
}

@end

Answer 2

为了让setValue:ForKey:正常工作，你的视图控制器必须符合NSKeyValueCoding协议。

试试这个：

-(void)goBack{
    [self.navigationController.parentViewController setFoo:@"bar"];
    [self.navigationController popViewControllerAnimated:YES];
}

别忘了在你的setFoo:方法中适当地保留/释放。您可能还需要键入cast parentViewController以避免任何警告。

Answer 3

将具有assign属性的母版的引用传递给detail视图。使用此引用在执行pop操作之前设置foo值。