ios - Swift 中的协议(protocol)和委托(delegate)

Question

我有两个 View Controller :“DiscoverViewController”和“LocationRequestModalViewController”。

用户第一次打开“DiscoverViewController”时，我会覆盖“LocationRequestModalViewController”，其中包含有关访问用户位置数据及其如何帮助用户的一些简介。

在“LocationRequestModalViewController”上有两个按钮:“不，谢谢”和“使用位置”。我需要将用户的响应发送回“DiscoverViewController”

我做了一些研究，发现委托(delegate)/协议(protocol)是最好的方法，所以我按照指南来实现它，但我留下了两个错误，无法弄清楚它们。

错误是:

在 DiscoverViewController 上

'DiscoverViewController' is not convertible to 'LocationRequestModalViewController'

在 LocationRequestModalViewController 上

'LocationRequestModalViewController' does not have a member name 'sendBackUserLocationDataChoice'

我已经在以下文件中标记了错误发生的位置:

DiscoverViewController.swift

class DiscoverViewController: UIViewController, UITextFieldDelegate, CLLocationManagerDelegate, LocationRequestModalViewControllerDelegate {

    func showLocationRequestModal() {
        var storyboard = UIStoryboard(name: "Main", bundle: nil)
        var locationRequestVC: AnyObject! = storyboard.instantiateViewControllerWithIdentifier("locationRequestVC")
        self.presentingViewController?.modalPresentationStyle = UIModalPresentationStyle.CurrentContext
        self.tabBarController?.presentViewController(locationRequestVC as UIViewController, animated: true, completion: nil)
    }

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
        let vc = segue.destinationViewController as LocationRequestModalViewController
        vc.delegate = self //This is where error 1 happens
    }

    func sendBackUserLocationDataChoice(controller: LocationRequestModalViewController, useData: Bool) {
        var enableData = useData
        controller.navigationController?.popViewControllerAnimated(true)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        showLocationRequestModal()
    }
}

LocationRequestModalViewController

protocol LocationRequestModalViewControllerDelegate {
    func sendBackUserLocationDataChoice(controller:LocationRequestModalViewController,useData:Bool)
}

class LocationRequestModalViewController: UIViewController {

    var delegate:LocationRequestModalViewController? = nil

    @IBAction func dontUseLocationData(sender: AnyObject) {
        self.dismissViewControllerAnimated(true, completion: nil)
    }

    @IBAction func useLocationData(sender: AnyObject) {
        delegate?.sendBackUserLocationDataChoice(self, useData: true) // This is where error #2 happens
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        //Modal appearance stuff here...
    }
}

Answer 1

答案就在你的问题本身。这两个错误都说明了确切原因。

问题 1

let vc      = segue.destinationViewController as LocationRequestModalViewController
vc.delegate = self //This is where error 1 happens

自身属于DiscoverViewController

但是您将委托(delegate)声明为:

var delegate:LocationRequestModalViewController? = nil

您需要将其更改为:

var delegate:DiscoverViewController? = nil

问题 2

同理，LocationRequestModalViewController没有向LocationRequestModalViewControllerDelegate确认，更改delegate声明。