Pass a class as a parameter?

Question

I have been lead to believe that it is possible to pass a class as a method parameter, but I'm having trouble implementing the concept. Right now I have something like:

- (id)navControllerFromView:(Class *)viewControllerClass                           title:(NSString *)title                       imageName:(NSString *)imageName {     viewControllerClass *viewController = [[viewControllerClass alloc] init];     UINavigationController *thisNavController =     [[UINavigationController alloc] initWithRootViewController: viewController];      thisNavController.tabBarItem = [[UITabBarItem alloc]                                   initWithTitle: title                                           image: [UIImage imageNamed: imageName]                                             tag: 3];     return thisNavController; } 

and I call it like this:

rootNavController = [ self navControllerFromView:RootViewController     title:@"Contact"     imageName:@"my_info.png" ]; 

What's wrong with this picture?

Answer 1

- (id)navControllerFromView:(Class)viewControllerClass 

It's just Class, without the asterisk. (Class isn't a class name; you're not passing a pointer to an instance of the Class class, you're passing the class itself.)

rootNavController = [ self navControllerFromView:RootViewController 

You can't pass a bare class name around like this—you have to send it a message. If you actually want to pass the class somewhere, you need to send it the class message. Thus:

rootNavController = [self navControllerFromView:[RootViewController class]                                           title:@"Contact"                                       imageName:@"my_info.png" ]; 

Answer 2

It looks like you've almost got it. You want to pass [RootViewController class] instead of RootViewController. That gives you a Class value. Also, I don't think you want your function to take a Class *, just a Class. It's not actually an Objective-C object.