Having trouble avoiding subclassing - ios

Question

I have an app with multiple view controllers. I am implementing a search bar to navigate a table view that is in each of these view controllers.
I have chosen to implement the search controller using a custom class, where I handle all the search logic. In order to make this possible, I am currently using a superclass from which each view controller inherits. I would like to know if there is a way for me to make this work without subclassing.
Here is the current implementation of my SearchController class:
class SearchController: NSObject, UISearchBarDelegate {
/* This is the trouble spot. If I change this to UIViewController?,
I get the compiler error "value of type UIViewController has no member tableView" */
weak var viewController: BaseViewController?
/*
... rest of SearchController implementation
includes methods that interact with view controller table views
*/
}
this is the BaseViewController class:
class BaseViewController: UIViewController {
let searchController = SearchController()
let tableView = UITableView(activityIndicatorStyle: UIActivityIndicatorViewStyle.gray)
/*
... rest of BaseViewController implementation
*/
}
To summarize, the issue I am having is that I have several view controllers with tableviews and I can't seem to make this work without creating a new base class that they can inherit from. Using UIViewController simply won't work because the UIViewController class does not have a tableView property built into it.
Any ideas?

Answer 1

You do not need to force all your viewControllers to subclasses BaseViewController. If the only requirement is for the viewController to have a tableView property then define a protocol with that requirement and make the relevant viewControllers implement that protocol.
Rewriting your example:
protocol BaseControllerProtocol: class {
var tableview: UITableView { get }
}
class SearchController: NSObject, UISearchBarDelegate {
//We store any class that implements the BaseControllerProtocol protocol
//Now you can use viewController.tableview
weak var viewController: BaseControllerProtocol?
//If you what to have UIViewcontrollers instances only use:
//weak var viewController: (UIViewController & BaseControllerProtocol)?
}
//An example of a viewcontroller that implements the BaseControllerProtocol
class ARandomViewController : UIViewController, BaseControllerProtocol {
var tableview: UITableView = UITableView()
}

Answer 2

I think you could still use UIViewController? if you assign its UITableView to your SearchViewController's private tableView calculated instance variable like so:
class SearchController: NSObject, UISearchBarDelegate {
weak var viewController: UIViewController?
fileprivate var _tableView: UITableView? {
if let vc = self.viewController {
for subview in vc.view.subviews {
if let tableView = subview as? UITableView {
return tableView
}
}
}
return nil
}
// Whatever methods interact with table view should now use self._tableView.
func doSomething() {
guard let tableView = self._tableView else { return }
// Do something with the tableView
}
}