将值传递给另一个类并在该视图控制器上显示

Question

I have two .swift classes. Test.swift and Start.swift .

Start.swift has a func called outputPercentage . See below.

var startClass = StartView()


class StartView: UIViewController {

    @IBOutlet var testProg: UILabel!

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

    func outputPercentage(pct: Int32) {
       let pctTxt = String(pct)
       print("Test Progress: ", pctTxt as Any)
       testProg.text = "Test" //pctTxt! + " / 100"
    }
}

testProg is a UILabel .

The func below is in Test.swift and passes an Int32 value back to the function above in Start.swift , like so:

var testClass = TestView()

class TestView {

  func sendpct() {
     var percentComplete : Int32 = 0;
     startClass.outputPercentage(pct: percentComplete)
  }

}

The line below gives me an " Unexpected optional nil " error.

testProg.text = pct_txt! + " / 100"

The UILabel is all set up correctly as I can set it elsewhere in the class, this error only occurs when the value has been passed from the other class.

How do I correctly output the value to my UILabel ?

Answer 1

It is better to use Delegate for your case.

In Start.swift

import UIKit

protocol StartDelegate: class {
    func outputPercentage(pct: Int32)
}

class StartView: UIViewController, StartDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view, typically from a nib.
        var test = Test()
        test.startDelegate = self
        test.sendpct()
    }

    // MARK: - Delegate Methods

    func outputPercentage(pct: Int32) {
        print(pct)
    }

}

In Test.swift

class Test {

    weak var startDelegate: StartDelegate?

    func sendpct() {
        if let startDelegate = startDelegate {
            var percentComplete : Int32 = 0;
            startDelegate.outputPercentage(pct: percentComplete)
        }
    }

}

Hope it helps!