如何只提供回调函数或块，而不是创建符合UIPickerViewDelegate的对象？

Question

我有两个ViewControllers，一个用于数据，另一个用于选择UIPickerView中的数据。因此，在根ViewController中，我想要获取选择器视图的委托。我在尝试这个：

RootViewController：

 let setReasonVc = self.storyboard?.instantiateViewController(withIdentifier: "setReasonVc") as! SetReasonViewController
 setReasonVc.providesPresentationContextTransitionStyle = true
 setReasonVc.definesPresentationContext = true
 setReasonVc.modalTransitionStyle = UIModalTransitionStyle.crossDissolve
 setReasonVc.modalPresentationStyle = UIModalPresentationStyle.overCurrentContext

 setReasonVc.pickerOptions.delegate = ???? // <- how to?

 self.present(setReasonVc, animated: true, completion: {})

ViewController选择：

class SetReasonViewController : UIViewController {

@IBOutlet weak var txtFieldJustificativa: UITextView!
@IBOutlet weak var pickerOptions: UIPickerView!

override func viewDidLoad() {

     }

}

Answer 1

Opt1:您需要在SetReasonViewControllervc中创建一个var

weak var delegate:RootVC?

那么当它出现的时候

setReasonVc.delegate = self

在此之后，viewDidLoad of SetReasonViewController

pickerOptions.delegate = delegate
/**pickerOptions.dataSource = delegate**/ un comment to make `SetReasonViewController ` the dataSource

class RootVC:UIViewController,UIPickerViewDelegate {
  //here implement didSelectRow
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

    }
 }

Opt2:另一个简单的选择是做

setReasonVc.loadViewIfNeeded()
setReasonVc.pickerOptions.delegate = self

警告当前代码

setReasonVc.pickerOptions.delegate = ???? // <- how to?

当您在vc加载之前访问选择器时(此时为零)，将导致崩溃，因此setReasonVc.loadViewIfNeeded()将修复它。

编辑：

class RootVC: UIViewController {

     func myNavigate() {

        let setReasonVc = self.storyboard?.instantiateViewController(withIdentifier: "setReasonVc") as! SetReasonViewController
        setReasonVc.providesPresentationContextTransitionStyle = true
        setReasonVc.definesPresentationContext = true
        setReasonVc.modalTransitionStyle = UIModalTransitionStyle.crossDissolve
        setReasonVc.modalPresentationStyle = UIModalPresentationStyle.overCurrentContext
        setReasonVc.callback = { (ind) in
            print(ind)
        }
        self.present(setReasonVc, animated: true, completion: {})
    }
}

class SetReasonViewController: UIViewController , UIPickerViewDelegate {

    var callback:((Int)->())?

    override func viewDidLoad() {
        super.viewDidLoad() 
       pickerOptions.delegate = self
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

        callback?(row)

    }

}

Answer 2

我认为您不能直接这样做，因为当您实例化VC时，视图还没有加载。

如果我是你，我会写SetReasonViewControllerDelegate

protocol SetReasonViewControllerDelegate : class {
    func reasonDidChange(to reason: String)
}

然后在RootVC中这样做

class RootViewController: UIViewController, SetReasonViewControllerDelegate {
    func reasonDidChange(to reason: String) {
        // do something here
    }
}

现在在SetReason VC中，您将self设置为delegate

class SetReasonViewController: UIViewController, UIPickerViewDelegate {
    let reasons = [...]
    weak var delegate: SetReasonViewControllerDelegate?

    override func viewDidLoad() {
        pickerOptions.delegate = self
    }
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        delegate?.reasonDidChange(to: reasons[row])
    }
    // other delegate methods...
}

当您显示设置原因VC时，您将self设置为它的委托：

setReasonVc.delegate = self

Answer 3

您需要有一个控制器，该控制器将为选择器填充数据，使其符合UIPickerViewDelegate，然后将其分配给setReasonVc.pickerOptions.delegate。您还需要通过遵循setReasonVc.pickerOptions.dataSource来设置UIPickerViewDataSource。