iOS代表取消通话失败

Question

I've got two view controllers, HomeViewController and AddViewController . HomeViewController is the delegate of AddViewController .

Problem is that when I hit the "Cancel" button in AddViewController , the call back to the delegate seems not to execute. Symptomatically, the Cancel button behaves as if it were not even wired up. Programmatically, breakpoints seem to indicate that control leaves the cancelButton method, yet never reaches addViewControllerDidCancel .

I believe everything is wired properly, and here's the relevant code:

From 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;

From HomeViewController.h:

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

From 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];

}

And from AddViewController.m:

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

Can someone spot my mistake?

Thanks!

Edit in response to answer 1 below:

Actually, I did this in my prepareFroSegue method in HomeViewController:

- (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;
    }

}

Answer 1

Your missing assigning the delegate object of your AddViewController instance, from what I can see it's still nil

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

EDIT:
You are calling this in your code:

[self.delegate addViewControllerDidCancel:self.thisActivity];

Ask yourself what is the value of delegate ? You have declared it, yes, but you have not set its value, so it must be nil . So when you instantiate your AddViewController you must set the delegate using the line I wrote before.