已分配的委托，但未調用函數

Question

嗨，大家好，我想在條件滿足時從FirstViewController觸發SecondViewController中的方法。 所以我用委托來做，我的代碼如下：

FirstViewController：

import UIKit
import CoreBluetooth
import Foundation

class BluetoothViewController: UIViewController, ValueChangedDelegate {


if (characteristic.UUID == CBUUID(string: "2AF0")){
        DataReceived.Single_Axis = Double(CharValue)


func peripheral(peripheral: CBPeripheral!, didUpdateValueForCharacteristic characteristic: CBCharacteristic!, error: NSError!) {
        let singleaxisview = SingeAxisViewController()
        singleaxisview.delegate = self
        singleaxisview.valueChangedNotifyEveryone()
        println("btfired")
    }

SecondViewController

import UIKit
import CoreGraphics

protocol ValueChangedDelegate
{
    func valueChanged(nValue : String)
}

class SingeAxisViewController: UIViewController {


var delegate : ValueChangedDelegate?


func valueChangedNotifyEveryone()
{
        println("hello")
    delegate?.valueChanged("changed value")
}

有人可以向我指出我錯過了什么嗎？

Answer 1

代替BTController!.delegate = self您將不得不使用FirstViewController的對象並設置委托，並且還需要初始化FirstViewController對象。 如果要實現，請參見以下示例代碼。 第一個視圖控制器實現委托方法，並在調用btnClicked時調用第二個視圖控制器，並在valueChanged方法中將響應返回給第一個視圖控制器

import UIKit

class FirstViewController: UIViewController, ValueChangedDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        lbl.text = "inital value"
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    // Get the new view controller using segue.destinationViewController.
    // Pass the selected object to the new view controller.
    }
    */

    @IBOutlet weak var lbl: UILabel!


    @IBAction func btnClicked(sender: AnyObject)
    {
        let secondViewController = SecondViewController()
        secondViewController.delegate = self
        secondViewController.valueChangedNotifyEveryone()
    }



    func valueChanged(nValue : String)
    {
        print(nValue)
        lbl.text = nValue
    }


}

第二個視圖控制器，它實現協議，並且還從valueChangedNotifyEveryone方法中調用protocol方法

import UIKit


protocol ValueChangedDelegate
{
    func valueChanged(nValue : String)
}


class SecondViewController: UIViewController {


    var delegate : ValueChangedDelegate?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    func valueChangedNotifyEveryone()
    {

        delegate?.valueChanged("changed value")
    }


    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}