Assigning to 'id' from incompatible type 'ViewController *const_strong'

Question

Throughout my app, I'm getting semantic issue warnings when I set ViewController.delegate = self. I have searched and found similar posts but none were able to solve my problem.

ViewController.m:

GameAddViewController *gameAddViewContoller = [[navigationController viewControllers] objectAtIndex:0];
gameAddViewContoller.delegate=self;

I get the error message when setting .delegate=self.

GameAddViewController.h:

@protocol GameAddViewControllerDelegate <NSObject>

- (void)gameAddViewControllerDidCancel:(GameAddViewController *)controller;
- (void)gameAddViewController:(GameAddViewController *)controller didAddGame:(Game *) game;

@end

@interface GameAddViewController : UITableViewController <GameAddViewControllerDelegate>
{
sqlite3         *pitchcountDB;
NSString        *dbPath;
}
@property (nonatomic, strong) id <GameAddViewControllerDelegate> delegate;
...
@end

ViewController.h:

#import "GameAddViewController.h"

@class ViewController;
@protocol ViewControllerDelegate <NSObject>
- (void)ViewControllerDidCancel:(ViewController *)controller;

@end
@interface ViewController : UIViewController <ViewControllerDelegate>
-(void) checkAndCreateFile;
@end

Can anyone point me in the right direction to resolve the warning messages?

score 82 · Accepted Answer · answered Mar 25 '12 at 16:09

82

At this line :

gameAddViewContoller.delegate=self;

Notice that self is of type ViewController which does NOT conform to the GameAddViewController protocol.

answered Mar 25 '12 at 16:09

giorashc

13,691
3
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1

What do I need to do to fix this. Is there something I need to change in the GameAddViewController protocol? – David L Mar 25 '12 at 21:30
Well, it depends on who you want to be your delegate. Who is implementing the GameAddViewController protocol – giorashc Mar 26 '12 at 07:39
GameAddViewController is the child of ViewController and I am implementing the gameAddViewControllerDidCancel method in ViewController. The error message is from the prepareForSegue method in ViewController when I set gameAddViewContoller.delegate=self. – David L Mar 26 '12 at 23:51
2

So do as @borrrden suggested. Conform the `ViewController` to the `GameAddViewControllerDelegate` delegate. – giorashc Mar 27 '12 at 07:25
37

OK, so I finally got it. I added this to my header file //#import "GameAddViewController.h" @interface ViewController : UIViewController @end// – David L Mar 28 '12 at 04:25
3

Or, this might help other people with similar problems: @interface myViewControllerName : UIViewController – Custom Bonbons Jul 28 '14 at 12:16
3

How did this get accepted and 72 votes? This answer just rewords XCode's warning and provides no solution. – SimpleJ Aug 08 '18 at 19:03

score 66 · Answer 2 · answered Oct 16 '13 at 22:58

66

For me what ended up happening is that I wasn't adding the delegate to the @interface on my header file

For example

@interface TheNameOfYourClass : UIViewController <TheDelegatorClassDelegate>

@end

answered Oct 16 '13 at 22:58

Raul Lopez

751
5
7

score 14 · Answer 3 · answered Mar 25 '12 at 16:03

14

You are putting the < GameAddViewControllerDelegate > in the wrong place. It doesn't go on GameAddViewController, it goes on ViewController.

answered Mar 25 '12 at 16:03

borrrden

33,256
8
74
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score 4 · Answer 4 · answered Jul 28 '14 at 12:29

4

This might help other people who are adding Multipeer Connectivity straight to a ViewController. At the top of myViewControllerName.h add '<MCSessionDelegate>':

@interface myViewControllerName : UIViewController<MCSessionDelegate>

answered Jul 28 '14 at 12:29

Custom Bonbons

1,609
2
12
17

score 1 · Answer 5 · answered Feb 13 '17 at 12:59

1

also, if you define your delegate on xx.m, but you use it in other class. you may get this problem. so, just put protocol define on xx.h, when it is needed.

answered Feb 13 '17 at 12:59

Michael Tangs

159
4

score 1 · Answer 6 · answered Jul 17 '19 at 15:58

If you have a hybrid project, the protocol in Swift and the assignment in Objective-C:

Swift declaration:

protocol BackgroundTasking {
    func beginTask(withName: String, expirationHandler handler: (()->Void)?)
    func endTask(withName: String)
}

Objective-C assignment:

@property (nonatomic) id<BackgroundTasking> backgroundTasker;

_backgroundTasker = [[BackgroundTasker alloc] init]; // WARNING

Assigning to '__strong id' from incompatible type 'BackgroundTasker *'

You need to declare the class (to remove this warning) and the functions (to make them accessible) as @objc for them to be correctly bridged.

Correct Swift declaration:

@objc protocol BackgroundTasking {
    @objc func beginTask(withName: String, expirationHandler handler: (()->Void)?)
    @objc func endTask(withName: String)
}

score 0 · Answer 7 · answered Feb 01 '19 at 13:43

0

On hybrid projects you should add your delegates on .h file instead of .m file

answered Feb 01 '19 at 13:43

oskarko

3,382
1
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Assigning to 'id' from incompatible type 'ViewController *const_strong'

7 Answers7