iOS protocol problem

[nashyo]

I'm receiving error "Cannot find protocol declaration for CheckmarkDelegate" in ContentAViewController.h. Why is this?

QuizTableViewController.h

#import <UIKit/UIKit.h>
#import "ContentAViewController.h"

@protocol CheckmarkDelegate <NSObject>
@required
- (void) processSuccessful: (BOOL)success;

@end

@interface QuizTableViewController : UITableViewController
{
    id <CheckmarkDelegate> delegate;
}

@property (retain) id delegate;

@end

QuizTableViewController.m

#import "QuizTableViewController.h"

@implementation QuizTableViewController
@synthesize delegate;

- (void) processComplete
{
    [self.delegate processSuccessful:YES];
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.tableView reloadData];
}

ContentAViewController.h

#import <UIKit/UIKit.h>
#import "QuizTableViewController.h"

@interface ContentAViewController : UIViewController <CheckmarkDelegate>

@end

ContentAViewController.m

#import "ContentAViewController.h"

@implementation ContentAViewController

- (void) processSuccessful: (BOOL) success
{
    NSLog(@"Process Succesful");
}

- (IBAction)OK:(id)sender 
{
    if ([answerAVal.text isEqualToString:@"CORRECT!"])
    {
        [self processSuccessful:YES];
    } else {
        
    [self dismissModalViewControllerAnimated:YES];
    }
}

 

[jiminaus]

Because QuizTableViewController.h is importing ContentAViewController.h.


Think about what happens when the compiler comes to compiling QuizTableViewController.m.

The first thing it encounters is #import "QuizTableViewController.h". So basically, that line is replaced with the contents of QuizTableViewController.h and compilation effectively continues with the first line of QuizTableViewController.h.

The second thing that happens is UIKit/Kit.h is imported in the same way.

The third thing that happens is #import "ContentAViewController.h" again in the same way.

Effectively we're now at the first line of "ContentAViewController.h. The #import <UIKit/UIKit.h> does nothing because UIKit/UIKIt.h has already been imported.

The #import "QuizTableViewController.h" is also ignored because QuizTableViewController.h has already (is being) imported.

Then the compiler get to the @interface ContentAViewController line in QuizTableViewController.h which references CheckmarkDelegate, but as you can see the compiler has never seen the @protocol CheckmarkDelegate at that point. So it complains.


For what you've posted, there's not need for QuizTableViewController.h to import ContentAViewController.h, so take it out.

 

[nashyo]

Confused

Because QuizTableViewController.h is importing ContentAViewController.h.


Think about what happens when the compiler comes to compiling QuizTableViewController.m.

The first thing it encounters is #import "QuizTableViewController.h". So basically, that line is replaced with the contents of QuizTableViewController.h and compilation effectively continues with the first line of QuizTableViewController.h.

The second thing that happens is UIKit/Kit.h is imported in the same way.

The third thing that happens is #import "ContentAViewController.h" again in the same way.

Effectively we're now at the first line of "ContentAViewController.h. The #import <UIKit/UIKit.h> does nothing because UIKit/UIKIt.h has already been imported.

The #import "QuizTableViewController.h" is also ignored because QuizTableViewController.h has already (is being) imported.

Then the compiler get to the @interface ContentAViewController line in QuizTableViewController.h which references CheckmarkDelegate, but as you can see the compiler has never seen the @protocol CheckmarkDelegate at that point. So it complains.


For what you've posted, there's not need for QuizTableViewController.h to import ContentAViewController.h, so take it out.

Still doesn't work.
Getting depressed.