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iOS委派取消呼叫失败

delegates objective-c ios

rattletrap99 · 技术社区 · 12 年前

我有两个视图控制器, HomeViewController 和 AddViewController . 家庭视图控制器 是的代表 添加视图控制器 .

问题是当我按下 添加视图控制器 ,对委托的调用似乎没有执行。有症状的是,“取消”按钮的行为就像它甚至没有连接一样。在编程上,断点似乎表明控件离开 cancelButton 方法,但从未达到 addViewControllerDidCancel .

我相信一切都连接正确,下面是相关代码:

从AddViewController.h:

#import <UIKit/UIKit.h>
#import "WMDGCategory.h"
#import "WMDGActivity.h"
@class HomeViewController;


@protocol AddViewControllerDelegate <NSObject>

-(void) addViewControllerDidSave;

-(void) addViewControllerDidCancel:(WMDGActivity *) activityToDelete;

@end

@interface AddViewController : UIViewController <UIPickerViewDataSource,UIPickerViewDelegate>


@property (nonatomic, weak) id <AddViewControllerDelegate> delegate;

从HomeViewController.h:

@interface HomeViewController : UITableViewController <UITableViewDataSource,UITableViewDelegate,AddViewControllerDelegate>

从HomeViewController.m:

-(void) addViewControllerDidSave
{
    NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread];
    [localContext MR_saveToPersistentStoreAndWait];
    [self.navigationController dismissViewControllerAnimated:YES completion:nil];
    [self refreshData];

}

-(void) addViewControllerDidCancel:(WMDGActivity *) activityToDelete
{
    [activityToDelete MR_deleteEntity];
    [self.navigationController dismissViewControllerAnimated:YES completion:nil];
    [self refreshData];

}

从AddViewController.m:

- (IBAction)cancelButton:(UIBarButtonItem *)sender
{
    [self.delegate addViewControllerDidCancel:self.thisActivity];
}

有人能发现我的错误吗?

谢谢

根据以下答案1进行编辑:

实际上,我在HomeViewController中的prepareFroSegue方法中这样做了:

- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
        NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread];
    if ([[segue identifier] isEqualToString:@"addModal"])
    {
        UINavigationController *navController = (UINavigationController *)segue.destinationViewController;
        AddViewController *avc = (AddViewController *)navController.topViewController;
        avc.delegate = self;
        WMDGActivity *addedActivity = (WMDGActivity *)[WMDGActivity MR_createInContext:localContext];
        avc.thisActivity = addedActivity;
    }

}

1 回复 | 直到 12 年前

Merlevede 12 年前

您缺少分配AddViewController实例的委托对象,从我可以看到它仍然 nil

myAddViewController.delegate = self;  // 'self' is an example, should be myHomeViewController instance

编辑:
您正在代码中调用此项:

[self.delegate addViewControllerDidCancel:self.thisActivity];

问问自己 delegate ? 你已经声明了它,是的,但是你没有设置它的值,所以它必须是 无 。因此,当您实例化 AddViewController 您必须使用我之前写的行设置代理。