如何正确覆盖UITableViewController子类的init（）？

Question

My UITableViewController subclass MatchTableViewController has the following properties:

class MatchTableViewController: UITableViewController {
    // MARK: - Properties
    var matches = [Match]()
    var dataModel: DataModel
    var apiModel: APIModel

I want to initialize dataModel and apiModel by overriding initializers.

override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
    // Init the DataModel
    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
    let managedContext = appDelegate.persistentContainer.viewContext
    guard let historyEntity = NSEntityDescription.entity(forEntityName: "History",
                                                         in: managedContext)
        else {
            fatalError("Failed to load the History entry")
    }
    self.dataModel = DataModel(historyEntity: historyEntity,
                               managedContext: managedContext)

    // Init the APImodel
    self.apiModel = APIModel()
    super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
    // Error here
}


override init(style: UITableView.Style) {
    // Init the DataModel
    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
    let managedContext = appDelegate.persistentContainer.viewContext
    guard let historyEntity = NSEntityDescription.entity(forEntityName: "History",
                                                         in: managedContext)
        else {
            fatalError("Failed to load the History entry")
    }
    self.dataModel = DataModel(historyEntity: historyEntity,
                               managedContext: managedContext)

    // Init the APImodel
    self.apiModel = APIModel()
    super.init(style: style)
    // Error here
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

Xcode gives me error 'super.init' isn't called on all paths before returning from initializer right after two super.init calls. I am not sure what I am missing here.

Answer 1

Problem is that if inside guard value isn't assigned, super.init(...) isn't called and non-optional variables aren't assigned as well. But you want to throw fatalError in else {...} so calling super.init(...) here wouldn't make any sense.

So first call super.init(...) and then do other stuff

override init(...) {
    super.init(...)
    ... // do other stuff
}

then make sure that you assign all non-optional global variables before you call super.init(...) . If don't (like your case), make these variables optional

var variable: Type?

Answer 2

override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
    super.init(style: style, reuseIdentifier: reuseIdentifier)

}

when override the init method required' initializer 'init(coder:)' must be provided by subclass of 'UITableViewCell'

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}