swift - 从不同的 ViewController 更改 UIButton

Question

我需要从另一个 UIViewController 更改 UIButton(status, title)

我试过下面的

import UIKit

class ViewController: UIViewController{

    @IBOutlet var B1: UIButton!
    @IBOutlet var B2: UIButton!

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


}

import Foundation
import UIKit

class View2: UIViewController {
    @IBAction func Dismiss(_ sender: Any) {
        h()

        dismiss(animated: true, completion: nil)
    }


    func h(){
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "VC") as? ViewController
        vc?.loadViewIfNeeded()

        print("c: ",vc?.B1.currentTitle ?? "")
        vc?.B1.setTitle("a", for: .normal)
        print("c: ",vc?.B1.currentTitle ?? "")
    }

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

输出是:

c:  V1B1
c:  a

它已更改(如输出所示)!但是当 View 消失时，它会返回到“V1B1”，这是我在 Main.storyboard

中输入的标题

我还尝试用协议(protocol)和委托(delegate)来改变它

import UIKit

class ViewController: UIViewController,TestDelegate {
    func t(NewT: UIButton) {
        NewT.setTitle("a", for: .normal)
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if let dd = segue.destination as? View2 {
            dd.d = self
            print("B1O: ",B1.currentTitle!)
        }
    }

    @IBOutlet var B1: UIButton!
    @IBOutlet var B2: UIButton!

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

import Foundation
import UIKit

protocol TestDelegate {
    func t(NewT: UIButton)
}

class View2: UIViewController {
var d: TestDelegate?

    @IBAction func Dismiss(_ sender: Any) {
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "VC") as? ViewController
        vc?.loadViewIfNeeded()
        print("B1: ",vc?.B1.currentTitle!)
            d?.t(NewT: (vc?.B1!)!)
        print("B1: ",vc?.B1.currentTitle!)

        dismiss(animated: true, completion: nil)
    }

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

输出:

B1O:  V1B1
B1:  Optional("V1B1")
B1:  Optional("a")

代码有什么问题？

即使 UIViewController 再次加载，我如何永久更改 UIButtons

Answer 1

import UIKit

class ViewController: UIViewController{

    @IBOutlet var B1: UIButton!
    @IBOutlet var B2: UIButton!

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

    open override func viewWillAppear(_ animated: Bool) {
        // Register to receive notification
        NotificationCenter.default.addObserver(self, selector: #selector(self.updateTitle), name: NSNotification.Name(rawValue: "buttonTitleUpdate"), object: nil)
        super.viewWillAppear(animated)
    }

    @objc func updateTitle() -> Void {
        print("c: ",B1.currentTitle ?? "")
        B1.setTitle("a", for: .normal)
        print("c: ",B1.currentTitle ?? "")
    }

}


import Foundation
import UIKit

class View2: UIViewController {
    @IBAction func Dismiss(_ sender: Any) {

        // Post a notification
        NotificationCenter.default.post(name: NSNotification.Name(rawValue: "buttonTitleUpdate"), object: nil)

        dismiss(animated: true, completion: nil)
    }

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