[Swift] Overriding a stored property

最近在用 Swift 開發時，遇到一個問題，在父類別宣告了一個變數，子類別要覆寫變數時，發生了 Overriding a stored property 這個問題，後來終於試出解法了，分享給大家。

先來看錯誤的程式碼 (Wrong Code)：

class C: UIViewController {

}

class A: UIViewController  {

    lazy var viewControllers: [UIViewController] = [
    ]
}

class B: A  {
  override var viewControllers: [UIViewController]  = [C()]
}
/// Error, Cannot override with a stored property 'viewControllers'

那我們如何解決呢？很簡單，只要用 get、set 就好了！ (Solution)

class C: UIViewController {

}

class A: UIViewController  {

    lazy var viewControllers: [UIViewController] = [
    ]
}

class B: A  {
    override var viewControllers: [UIViewController] {
      get {return [C()]}
      set {}
    }
}

另一個解決方法是用 func，再 override func，也是可以達到異曲同工之妙！ (Alternative Solution)

class C: UIViewController {

}

class A: UIViewController  {

    lazy var viewControllers: [UIViewController] = getViewControllers()

    func getViewControllers() ->  [UIViewController]{
    }
}

class B: A  {
    override func getViewControllers() ->  [UIViewController]{
      return [C()]
    }
}