Question

I know how to do it in java but im stubling in objetice-c

In java I would have an interface like this:

public interface Car {
    public void startCar();
}

and the a class which would implement this interface:

public class SomeCarImpl implements Car {
   public void startCar() {
      System.out.println("starting the car...");
   }
}

and now I would be able to this in my main class

public void MainClass {
   public static void main(String [] args) {
       Car myCar = new SomeCarImpl();
       car.startCar();
   }
}

Now here I’m getting in trouble in objective-c. The first two things are easily made with protocols but when I want to call it like this, nothing happens

//header
id <Car> *myCar;

//instance
myCar = [[SomeCarImpl alloc] init];

//calling and nothing happens
[myCar startCar];

I hope you can understand my problem…and help me 🙂

//edit here is the code

@interface SomeCarImpl:NSObject<Car>
@end

@implementation SomeCarImpl
-(void)startCar{
NSLog(@"run");
}
@end  

@protocol Car <NSObject>
-(void)startCar;
@end



@interface DetailViewController:UIViewController<UISplitViewControllerDelegate> {
IBOutlet UIButton *runButton;
id<Car> myCar;
}
@property(strong, nonatomic)IBOutlet UIButton *runButton;
@property(strong, nonatomic)id<Car> myCar;
@end

and finally (detailViewController.myCar = [[SomeCarImpl]alloc]init] is called in the tableView beforehand)

-(IBAction)runButton:(id)sender {
[myCar startCar];
}

Answer 1

Your Java code would vaguely translate into something like this:

//public interface Car {
//    public void startCar();
//}

@protocol Car
- (void)startCar;
@end

//public class SomeCarImpl implements Car {
//    public void startCar() {
//        System.out.println("starting the car...");
//    }
//}

@interface SomeCarImpl : NSObject<Car>

@end

@implementation SomeCarImpl

- (void)startCar {
    NSLog(@"starting the car...");
}

@end

// Car myCar = new SomeCarImpl();
// car.startCar();
id<Car> myCar = [[SomeCarImpl alloc] init];
[myCar startCar];

In your ObjC code, you need to remove the asterisk from this line:

id <Car> *myCar;

Because the type id is already a pointer (although I don’t think this is not the root of your problem).