In my MyClass.h, I have this:
#import "AClass.h"
#interface MyInterface : UIViewController <UIScrollViewDelegate>
#property (strong, nonatomic) AClass *ptr;
#end
But when I compile it, I get an error saying Unknown type name 'AClass' , did you mean 'BClass'.
What I don't understand it I already have "#import "AClass.h", how can I fix my error?
In AClass.h, I have
#interface AClass : UICollectionViewFlowLayout
#end
And both AClass.h and MyClass.h are in the same directory.
Thank you.
(This answer is obsolete since the question was changed including the displayed code)
It's your headerfile, right? So don't import yourself.
In MyClass.m you need #import "MyClass.h", but not in the header file of MyClass itself.
Related
In Objective-C you can generally re-declare a readonly property as readwrite in a class extension like this:
#interface PubliclyImmutablePrivatelyMutableClass : NSObject
#property (readonly, nonatomic) SomeStateEnum someState;
#end
// In "PubliclyImmutablePrivatelyMutableClass+Private.h"
// or "PubliclyImmutablePrivatelyMutableClass.m"
#interface PubliclyImmutablePrivatelyMutableClass()
#property (readwrite, nonatomic) SomeStateEnum someState;
#end
// In "PubliclyImmutablePrivatelyMutableClass.m"
#implementation PubliclyImmutablePrivatelyMutableClass #end
If, however, I introduce a property in a class extension as readonly and try to re-declare it as readwrite in a second one, Xcode 10’s Clang gives me a compiler error:
#interface ClassWithPrivateImmutableInternallyMutableProperty : NSObject
// any public API
#end
// In "ClassWithPrivateImmutableInternallyMutableProperty+Private.h"
#interface ClassWithPrivateImmutableInternallyMutableProperty()
#property (readonly, nonatomic) SomePrivateStateEnum somePrivateState;
#end
// In "ClassWithPrivateImmutableInternallyMutableProperty.m"
#interface ClassWithPrivateImmutableInternallyMutableProperty()
#property (readwrite, nonatomic) SomePrivateStateEnum somePrivateState; // error: property has a previous declaration
#end
#implementation ClassWithPrivateImmutableInternallyMutableProperty
// other API
#end
Now I wonder:
Is the compiler error a bug/regression in Clang or a deliberate feature?
If it’s a bug, is there another workaround than manually implementing the setter?
I believe that this is correct behavior from the compiler.
In the second example you are using two class continuation categories with the same name () to declare the same property on two occasions. It is effectively the same as declaring the same property name twice in the same extension.
Note that this differs from the first example, in which the property is declared first in the header and then re-declared in a single class continuation category named ().
If I am right, then the answer is to mark the '+private' class extension with a name like (Private) instead of ():
#interface ClassWithPrivateImmutableInternallyMutableProperty(Private)
And also if you have any implementation for the private extension:
#implementation ClassWithPrivateImmutableInternallyMutableProperty(Private)
I hope that helps!
I know this is a common subject but I did not find any answer to help me out with this problem.
Well, I do have (by now) 3 .h files,
One is the superclass of the two others.
Superclass : ExportationAutoFilterNew
#import <Foundation/Foundation.h>
#import <HIDDEN/PluginFilter.h>
#class MyOutlineView;
#interface ExportationAutoFilterNew : PluginFilter
#property (assign, nonatomic) NSUserDefaults *prefs;
#property (assign, nonatomic) MyOutlineView *databaseOutline;
#end
Then, sub-classes : DetectNewExams & ExportExams
#import <Foundation/Foundation.h>
#import <HIDDEN/PluginFilter.h>
#import "ExportationAutoFilterNew.h"
#interface DetectNewExams : ExportationAutoFilterNew
- (void)detectExams:(NSDate*)currentDate timeInterval:(double)timeInterval afterExitHidden:(BOOL)check;
And
#import <Foundation/Foundation.h>
#import <HIDDEN/PluginFilter.h>
#import "ExportationAutoFilterNew.h"
#interface ExportExams : ExportationAutoFilterNew
- (void)exportExams:(NSManagedObject*)curObj;
The .m goes like this
Superclass : ExportationAutoFilter
#import <HIDDEN/PreferencesWindowController.h>
#import <HIDDEN/browserController.h>
#import "ExportationAutoFilterNew.h"
#import "DetectNewExams.h"
#implementation ExportationAutoFilterNew
Xcode for this file (ExportationAutoFilterNew.m) :
Instance method '-detectExams:timeInterval:afterExitHidden:' not found (return type defaults to 'id')
For the call of :
[self detectExams:lastExportDate timeInterval:0 afterExitHidden:YES];
Sub-classes : DetectNewExams
#import <HIDDEN/PreferencesWindowController.h>
#import <HIDDEN/browserController.h>
#import "DetectNewExams.h"
#import "ExportExams.h"
#implementation DetectNewExams
In this file (DetectNewExams.m), Xcode says :
Instance method '-exportExams:' not found(return type defaults to 'id')
Calling :
[self exportExams:curObj];
And then : ExportExams
#import <HIDDEN/PreferencesWindowController.h>
#import <HIDDEN/browserController.h>
#import "ExportExams.h"
#implementation ExportExams
I'm wasting hours on this thing and I can't figure the problem out, may you help me ? I looked up for compiling circle but I don't think I created one with my imports ..
Thanks.
Your interface is not properly declared. Try this.
#interface ExportationAutoFilterNew : PluginFilter
#property (nonatomic) NSUserDefaults *prefs;
#property (nonatomic) MyOutlineView *databaseOutline;
#end
Now that you have posted the actual error, this becomes more clear. But you still haven't posted enough context.
Instance method '-detectExams:timeInterval:afterExitHidden:' not found (return type defaults to 'id')
That means that the method declaration hasn't been seen at the time the code was compiled or the method is declared on some class that whatever was being called is not an instance of.
Since you haven't shown the call site or the declaration of the variable being called, this is a guess. The method is declared on the DetectNewExams class. I'd bet you have a variable that points to an instance of ExportationAutoFilterNew and, therefore, the compiler is correctly warning that the method doesn't exist on the class.
I have code like following:
#import "ViewModelBase.h"
#interface ViewControllerA : UIViewController
#property (nonatomic, strong) ViewModelBase* viewModel;
#end
Then I need to do something like following:
#import "ViewControllerA.h"
#class ViewModelSubclass;
#interface ViewControllerB : ViewControllerA
#property (nonatomic, strong) ViewModelSubclass* viewModel;
#end
Where ViewModelSubclass.h is not supposed to be imported to ViewControllerB.h, only to .m file.
However, ViewModelSubclass is supposed to be subclass of ViewModelBase.
This is done to hide interface of ViewModelSubclass from clients of ViewControllerB.
How do I solve "Property type 'ViewModelSubclass*' is incompatible with type 'ViewModelBAse*' inherited from ViewControllerA" warning?
Or what is a better way to do it?
don't use like this
#import<ViewControllerA.h>
try to use like
#import "ViewControllerA.h"
I think it will solve your problem
I am stuck with this problem. I have the following .h file:
#import <UIKit/UIKit.h>
#protocol MapSettingsViewDelegate
- (void)settingsDidUpdate:(BOOL)scheme;
#end
#interface MapSettingsViewController : UIViewController
#property (nonatomic, assign) id <MapSettingsViewDelegate> delegate;
#property (nonatomic, strong) IBOutlet UINavigationBar *navBar;
#property (nonatomic, strong) IBOutlet UINavigationItem *titleItem;
#property (nonatomic, strong) IBOutlet UITableView *TableView;
- (id)init;
- (IBAction)saveAction:(id)sender;
#end
When I declare the following:
#interface MapViewController : UIViewController <MapSettingsViewDelegate>
The compiler complains with the following message:
Cannot find protocol declaration for 'MapSettingsViewDelegate'
I have the same kind of delegate declaration in other files in the same project that are compiled without a glitch. I spent the last four hours trying to figuring out what I am doing wrong. Cleaning the project does not nothing.
Problem solved. As suggested in this answer, I created a new class with a different name and copied all coded from the previous class. Worked flawlessly. It seems XCode lost track of something.
You are running into preprocessor problems. Both of your classes import each other. I think you can solve this by adding #class below your protocol declaration as shown below; and moving your #import "mapViewController.h" line into MapSettingsViewController.m file. The #class tells the compiler that you will include the class content somewhere else (in the .m file).
Note that, on the top of your MapViewController.h class file you can include #import "MapSettingsViewController.h" just like normal. Hope this help. I ran into the same problem myself earlier.
#import <UIKit/UIKit.h>
#protocol MapSettingsViewDelegate
- (void)settingsDidUpdate:(BOOL)scheme;
#end
#class MapViewController
#interface MapSettingsViewController : UIViewController
#property (nonatomic, assign) id <MapSettingsViewDelegate> delegate;
...
...
Import the MapSettingsViewController.h file
Sorry, couldn't find a more appropriate title.
In My code I have two classes which should know of each others existence. So I use an instance variable which points to the other class. For that to work (I guess?) the other classes headers file should be imported so it knows which methods it has and such.
Here is my code (stripped down)
MainMenuController.h:
#import <Cocoa/Cocoa.h>
#import "IRCConnection.h"
#interface MainMenuController : NSViewController {
IRCConnection *ircConnection;
}
#property (strong) IRCConnection *ircConnection;
#end
IRCConnection.h:
#import <Foundation/Foundation.h>
#import "MainMenuController.h"
#interface IRCConnection : NSObject {
MainMenuController *mainMenuController;
}
#property (strong) MainMenuController *mainMenuController;
#end
As you can see they both import each other, but this creates an error (Unknown type name 'IRCConnection') in one, and in the other Unknown type name 'MainMenuController'.
However when the connection is just one way (e.g. only MainMenuController knows about IRCConnection) and thus there is only an import statement in one of the two, it works fine.
How can I have them to know about each other? In both ways.
Hope this question makes any sense.
you could remove the import from IRCConnection.h and use a #class statement instead.
like this:
#import <Foundation/Foundation.h>
#class MainMenuController;
#interface IRCConnection : NSObject {
then add a #import "MainMenuController.h" to IRCConnection.m
In the header, use forward declaration:
#class IRCConnection;
#interface MainMenuController : NSViewController {
IRCConnection *ircConnection; // ok
}
In the source file (.m), do #import.
You cannot have circular imports. You need to break them up, or introduce some forward declarations.