Type arguments cannot be applied to non-class type 'id'

Question

I am new to ObjectiveC and have been working for few years in Swift. Therefore, I don't understand the below explained error in Xcode:

Type arguments cannot be applied to non-class type 'id'

My Protocol:

@protocol ExampleProtocol<NSObject>
@required
        
-(NSString *)title;
-(NSString *)album;
    
@end

My implementation in the MyService.h file:

@interface MyService : NSObject 
@property (nonatomic, assign, readwrite) id<ExampleProtocol> delegate;
@end

The error occurs in the line:

> @property (nonatomic, assign, readwrite) id<ExampleProtocol> delegate;

Additionally:

• I have imported the required file .h in which the ExampleProtocol code is located in the MyService.m file
• Added the @class ExampleProtocol; in my MyService.h file at the top.

Also tried:

• Creating a Swift protocol with @objc and : class imported over the app-Bridging.h gives me the same result with the same error message.

• Clean build

• Clean build folder (removed derived data)

  The only thing that did work was to remove the line from the public interface to the private. This doesn't make sense. I wan't to set the delegate from another class and creating a public setter which set the private delegate is ugly workaround.

Any suggestion would be helpfull. I would like to understand why this happens. There are a lot of other protocols in my project written in ObjectiveC which work fine.

Answer 1

ExampleProtocol is a protocol, not a class. You don't need it if you import the header. If you don't import the header, it should be @protocol ExampleProtocol;