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

You haven't explained any problem with the code you've posted. What doesn't work? What are you expecting to happen? The only thing I can think of so far is that you might want to pass [RootViewController class] instead of just RootViewController. Also, your formatting is killing me.

Answer 2

- (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 a 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 3

Hey! 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.