Cocoa Swift - 从两个 ViewController 传递数据答案

【问题标题】：Cocoa Swift - Pass data from two ViewControllersCocoa Swift - 从两个 ViewController 传递数据
【发布时间】：2021-11-30 08:08:42
【问题描述】：

我正在使用协议和委托将数据从一个 viewController 传递到另一个 viewController，但是当我单击发送时，它只会更改 viewController 而不会传递数据。

有人知道如何将数据从 ViewController B 返回到 ViewController A 吗？

它编译和工作正常，但没有记录，所以我不知道它是否有效。

//  FirstViewController.swift

import Cocoa

class FirstViewController: NSViewController, DataEnteredDelegate {


    @IBOutlet weak var buttonPasswordState: NSView!

    @IBOutlet weak var label: NSTextField!
    
    
    
    override func viewDidLoad() {
        super.viewDidLoad()

   }


@IBAction func buttonPasswordState(_ sender: Any) {
        
        if let controller = self.storyboard?.instantiateController(withIdentifier: "SecondViewController") as? SecondViewController {
        self.view.window?.contentViewController = controller
        }
        
    }
    
    

    func userDidEnterInformation(info: String) {
            label.stringValue = info
        }


}

//  SecondViewController.swift

import Cocoa

class SecondViewController: NSViewController {

    @IBOutlet weak var buttonContinue: NSButton!

    weak var delegate: DataEnteredDelegate? = nil
    
    @IBOutlet weak var textField: NSTextField!
    

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

@IBAction func buttonContinue(_ sender: Any) {
        
        if let controller = self.storyboard?.instantiateController(withIdentifier: "FirstViewController") as? FirstViewController {
        self.view.window?.contentViewController = controller
            

            delegate?.userDidEnterInformation(info: textField.stringValue)
        }
        
       
    }
    
    
    
}


protocol DataEnteredDelegate: class {
    func userDidEnterInformation(info: String)
}

【问题讨论】：

如果某些东西按预期工作，为什么要记录它？如果需要确定，请尝试在带断点的调试中运行。
controller.delegate = self

标签： swift cocoa nsviewcontroller pass-data

【解决方案1】：

你在这里创建了一个全新的 SecondViewController 实例，在你展示它之前没有配置或更改：

    if let controller = self.storyboard?.instantiateController(withIdentifier: "SecondViewController") as? SecondViewController {
    // TODO something like controller.configureWith(dataFromFirstVC)... e.g. controller.delegate = self
    self.view.window?.contentViewController = controller
    }

当您想返回您的 FirstViewController 时，再次创建一个全新的 FirstViewController 实例，您不会回调同一个实例 - 那是您的委托：

    if let controller = self.storyboard?.instantiateController(withIdentifier: "FirstViewController") as? FirstViewController {
    self.view.window?.contentViewController = controller
        // controller is not the same object as delegate

        delegate?.userDidEnterInformation(info: textField.stringValue)
    }

【讨论】：

【解决方案2】：

我想这会对你有所帮助。

class FirstViewController: UIViewController, DataPassProtocol {

    override func viewDidLoad() {
        super.viewDidLoad()
    
        DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
            self.fireSecondViewController()
        }
    
    }

    func fireSecondViewController() {
        let secondViewController = SecondViewController()
        secondViewController.delegateFirstViewController = self
    }

    // MARK: - protocol methods
    func dataCaptured(with value: SampleData) {
        // we captured data from secondViewController
        print("data : \(value.temp)")
    }
}

class SecondViewController: UIViewController {

    weak var delegateFirstViewController: DataPassProtocol?

    override func viewDidLoad() {
        super.viewDidLoad()
    
        DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
            self.sendSomeDataToFirstViewController()
        }
    
    }

    func sendSomeDataToFirstViewController() {
        delegateFirstViewController?.dataCaptured(with: SampleData(temp: "Tadaaaaaaa"))
    }
}

struct SampleData {
    let temp: String
}

protocol DataPassProtocol: AnyObject {
    func dataCaptured(with value: SampleData)
}

【讨论】：