So I have one class CommentViewController.h in which I have
#import "FirstViewController.h"
#protocol CommentViewControllerDelegate;
#interface CommentViewController : UIViewController {
id <CommentViewControllerDelegate> delegate;
}
#property (nonatomic, assign) id <CommentViewControllerDelegate> delegate;
- (IBAction)submit:(id)sender;
-(IBAction)cancel:(id)sender;
#end
#protocol CommentViewControllerDelegate
-(void)commentViewControllerDidFinish:(CommentViewController *)controller;
#end
I synthesized delegate in the implementation
I try to access the protocol in FirstViewController.h:
#import "CommentViewController.h"
#interface FirstViewController : UIViewController <CommentViewControllerDelegate>
And in the implantation of FirstViewController :
- (void)commentViewControllerDidFinish:(CommentViewController *)controller {
[self dismissModalViewControllerAnimated:YES];
}
The error appears on this line:
#interface FirstViewController : UIViewController <CommentViewControllerDelegate>
Error: Cannot find protocol declaration for 'CommentViewControllerDelegate'; did you mean 'UISplitViewControllerDelegate'?
Am I missing something? I always have trouble with protocols and delegates.
You have a loop in your include files.
Remove this line from CommentViewController.h:
#import "FirstViewController.h"
It's not referenced in that header file, and if it were, you could simply put:
#class FirstViewController;
instead of including the whole file.
Related
I have two classes DetailViewController and Substitution, I would use the Substitution class methods but I get this error:
No visible #interface "Substitutions" declares the selector "Crypt ::"
DetailViewController.h
#import <UIKit/UIKit.h>
#import "Substitutions.h"
#interface DetailViewController : UIViewController
#property (weak, nonatomic) IBOutlet UITextField *tvC;
- (IBAction)bCrypter:(id)sender;
#property (nonatomic, strong) Substitutions * s;
DetailViewController.m
#import "DetailViewController.h"
#implementation DetailViewController
#synthesize s;
#synthesize tvC;
- (IBAction)bCrypter:(id)sender
{
s = [[Substitutions alloc]init];
[s Crypter:tvC.text :1]; <-- No visible #interface "Substitutions" declares the selector "Crypter::"
//NSLog(#"%#",tvC.text);
}
Substitutions.h
#interface Substitutions : NSObject
+ (NSString*)Crypter:(NSString*)msg :(id)cles;
#end
Substitutions.m
#import "Substitutions.h"
#implementation Substitutions
+ (NSString*)Crypter:(NSString*)msg :(id)cles
{
NSLog(#"%#",msg);
return #"";
}
Because Crypter is class method not instance method so you should call directly with class name not need to create instance for call method.
Ex.
[Substitutions Crypter:tvC.text :1];
I am getting new warning on my old OSX app. I am using OSX 10.10 and I am not quite sure where the problem is. Can someone help?
The actual warning is Property type 'id is incompatible with type id inherited from NSTextField
#import <Cocoa/Cocoa.h>
#import "HyperlinkTextFieldDelegate.h"
#interface HyperlinkTextField : NSTextField <NSTextFieldDelegate>
#property (assign) id <HyperlinkTextFieldDelegate> delegate; <--- warning showing up here
#end
The main implementation is
#interface HyperlinkTextField ()
#property (nonatomic, readonly) NSArray *hyperlinkInfos;
#property (nonatomic, readonly) NSTextView *textView;
- (void)_resetHyperlinkCursorRects;
#end
#define kHyperlinkInfoCharacterRangeKey #"range"
#define kHyperlinkInfoURLKey #"url"
#define kHyperlinkInfoRectKey #"rect"
#implementation HyperlinkTextField
#synthesize delegate;
And the delegate file is
#import <Foundation/Foundation.h>
#protocol HyperlinkTextFieldDelegate <NSObject>
- (void) barLinkClicked: (id) sender;
#end
NSTextField already has a delegate property, and it is typed as id<NSTextFieldDelegate>. Thus, your HyperinkTextField, which is a subclass of NSTextField, inherits this property, just as the error message clearly tells you. You cannot override this inherited property and type it as id<HyperlinkTextFieldDelegate> where that is a different type.
I have custom UIView class GestureView. I have a forward declaration for this class and it's delegate below. I have imported GestureView.h in .m file. This works fine but iOS gives warning message saying "Cannot find protocol definition for GestureViewDelegate". If I remove forward declaration it gives same warning message as error. I don't want to import GestureView.h from ContainerViewController.h as I usually imports stuffs in .m file. Could someone please explain what's wrong in following class structure?
ContainerViewController.h
#import <UIKit/UIKit.h>
#class DividerView;
#class GestureView;
#protocol GestureViewDelegate;
#interface ContainerViewController : UIViewController<GestureViewDelegate>
#property (strong, nonatomic) IBOutlet GestureView *topContentView;
#end
GestureView.h
#import <UIKit/UIKit.h>
#protocol GestureViewDelegate;
#interface GestureView : UIView
- (void)initialiseGestures:(id)delegate;
#end
#protocol GestureViewDelegate <NSObject>
#required
- (void)GestureView:(GestureView*)view handleSignleTap:(UITapGestureRecognizer*)recognizer;
#end
I like that you're trying to avoid imports in header files: very good practice. However, to fix your bug you can just make your code even better! In my opinion it's not really necessary that your ContainerViewController class outwardly declares that it supports GestureViewDelegate protocol, so you should move this into your implementation file. Like so:
GestureView.h
#import <UIKit/UIKit.h>
#protocol GestureViewDelegate;
#interface GestureView : UIView
- (void)initialiseGestures:(id <GestureViewDelegate>)delegate;
#end
#protocol GestureViewDelegate <NSObject>
#required
- (void)gestureView:(GestureView *)view handleSingleTap:(UITapGestureRecognizer *)recognizer;
#end
ContainerViewController.h
#import <UIKit/UIKit.h>
#class GestureView;
#interface CollectionViewController : UIViewController
// this property is declared as readonly because external classes don't need to modify the value (I guessed seen as it was an IBOutlet)
#property (strong, nonatomic, readonly) GestureView *topContentView;
#end
ContainerViewController.m
#import "ContainerViewController.h"
#import "GestureView.h"
// this private interface declares that GestureViewDelegate is supported
#interface CollectionViewController () <GestureViewDelegate>
// the view is redeclared in the implementation file as readwrite and IBOutlet
#property (strong, nonatomic) IBOutlet GestureView *topContentView;
#end
#implementation ContainerViewController
// your implementation code goes here
#end
Try this way, and please reply if it works or not.
GestureView.h
#import <UIKit/UIKit.h>
#protocol GestureViewDelegate <NSObject>
#required
- (void)GestureView:(GestureView*)view handleSignleTap:(UITapGestureRecognizer*)recognizer;
#end
#interface GestureView : UIView
- (void)initialiseGestures:(id)delegate;
#end
ContainerView.h
#import <UIKit/UIKit.h>
#class DividerView;
#class GestureView;
/*#protocol GestureViewDelegate;*/ //NO NEED TO WRITE THIS
#interface ContainerViewController : UIViewController<GestureViewDelegate>
#property (strong, nonatomic) IBOutlet GestureView *topContentView;
#end
I have defined a protocol in a separate file (myProtocol.h). Here is the code for it:
#import <Foundation/Foundation.h>
#protocol myProtocol <NSObject>
-(void) loadDataComplete;
#end
Now I want to call this method so I have done the following code:
firstViewController.h:
#import "myProtocol.h"
#interface firstViewController : UIViewController{
id <myProtocol> delegate;
}
#property (retain) id delegate;
-(void) mymethod;
firstViewController.m
#implementation firstViewController
#synthesize delegate;
- (void)viewDidLoad {
[self mymethod];
}
-(void) mymethod {
//some code here...
[delegate loadDataComplete];
}
I have another file where the protocol is also utilized:
secondViewController.h:
#import "myProtocol.h"
#interface secondViewController : UIViewController<myProtocol>{
}
secondViewController.m:
-(void) loadDataComplete{
NSLog(#"loadDataComplete called");
}
but my secondViewController is not calling the protocol methad. Why is it so? Any suggestion will be appreciated.
First, as #Abizern suggested, try to reformat your code a little bit. Use capital letter for classes. Said this here the solution for your answer.
This is the protocol. I would name it like FirstViewControllerDelegate since the class that implements the object is a delegate for FirstViewController.
#import <Foundation/Foundation.h>
#protocol MyProtocol <NSObject>
- (void)doSomething;
#end
This is SecondViewController.
#import <UIKit/UIKit.h>
#import "MyProtocol.h"
#interface SecondViewController : UIViewController <MyProtocol>
#end
#implementation SecondViewController
// other code here...
- (void)doSomething
{
NSLog(#"Hello FirstViewController");
}
#end
This is FirstViewController.
#import <UIKit/UIKit.h>
#interface FirstViewController : UIViewController
// it coud be better to declare these properties within a class extension but for the sake of simplicity you could leave here
// the important thing is to not declare the delegate prop with a strong/retain property but with a weak/assign one, otherwise you can create cycle
#property (nonatomic, strong) SecondViewController* childController;
#property (nonatomic, weak) id<MyProtocol> delegate;
#end
#implementation FirstViewController
// other code here...
- (void)viewDidLoad
{
[super viewDidLoad];
self.childController = [[SecondViewController alloc] init];
self.delegate = self.childController; // here the central point
// be sure your delegate (SecondViewController) responds to doSomething method
if(![self.delegate respondsToSelector:#selector(doSomething)]) {
NSLog(#"delegate cannot respond");
} else {
NSLog(#"delegate can respond");
[self.delegate doSomething];
}
}
#end
For the sake of completeness, be sure to understand the delegate pattern means. Apple doc is your friend. You could take a look at the-basics-of-protocols-and-delegates to have a basic intro on the argument. Furthermore, SO search allows you to find a lot of answers on the topic.
Hope that helps.
I have a protocol like this:
#import <Foundation/Foundation.h>
#protocol Prot1 <NSObject>
#required
- (void)methodInProtocol;
#end
This is a protocol for a delegate I want to store in a class like this:
#import <Cocoa/Cocoa.h>
#class Prot1;
#interface Class1 : NSObject
#property (nonatomic, strong) Prot1 *delegate;
- (void)methodInClass;
#end
The implementation for this class is like this:
#import "Class1.h"
#import "Prot1.h"
#implementation Class1
#synthesize delegate;
- (void)methodInClass {
[delegate methodInProt];
}
#end
When I build these pieces of code, I get the following error:
Receiver type 'Prot1' for instance message is a forward declaration
What is wrong here? I did understand that I have to do a forward declaration via #class for the protocol and I thought I only had to #import the protocol, in the class implementation... Isn't that right?
As it isnt a class, you have to define it as what it is - a protocol ;)
Use forward declaration: #protocol Prot1;;
And use the property like that:
#property (nonatomic, strong) id<Prot1> delegate;