尝试分配新值时,编译器会抛出错误:
Cannot assign to immutable expression of type 'Bool?'
我上课了:
class Setting { struct Item { var text: String var selected: Bool? init(withText text: String) { self.text = text self.selected = nil } var items: Any init(items:Any) { self.items = items } }
在prepareForSegue的源视图控制器中:
let item = Setting.Item(withText: user.description) let setting = Setting(items: [item]) destinationViewController.setting = setting
在目标视图控制器中:
class DestinationViewController: UITableViewController { var setting: Setting! override func viewDidLoad() { super.viewDidLoad() //this works _ = (setting.items as! [Setting.Item])[index].selected // this throws the error (setting.items as! [Setting.Item])[index].selected = false } }
我将项目声明为Any,因为它可以包含[Items]或[[Items]].
如何使变量选择为可变?