在Swift UIView XIB中全局初始化变量为'nil'？

Question

I have globally initialised variable inside a UIView class.

The variable is statusLabel as string. I have assigned a value for statusLabel in Pickerview didSelectRow delegate method. There i'm getting the value for string. However When the delegate finishes the value of string changes to nil

It's all same for all other Globally initialised variable. What Could be the reason?

Thanks in Advance

class CustomPickerMenu: UIView,UIPickerViewDataSource,UIPickerViewDelegate
{
    var statusLabel = String()

    var pickerArray = [String]()

    required init?(coder aDecoder: NSCoder)
    {
        pickerArray = ["None","Connections","All"]
        super.init(coder: aDecoder)
         print("Awake with coder")

    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
    {
        if(row == 0)
        {
            statusLabel = pickerArray[row]
        }
        if(row == 1)
        {
            statusLabel = pickerArray[row]
        }
        if(row == 2)
        {
            statusLabel = pickerArray[row]
        }
      print("statusLabel : " + statusLabel)
    }

    @IBAction func saveStatus(_ sender: Any)
    {   
        delegate?.statusChange(controller: self, text:statusLabel)
        self.delegate?.showNavigationController(controller: self)

        print("statusLabel : " + statusLabel)
    }

here is the output for statusLabel during didselectrow delegate(1st three outputs) and save status(last output)

Answer 1

I found the solution, more than that it was a mistake. the class the I used "CustomPickerMenu" got called more than one time. During init(frame) and init(decoder). Thats the reason the value of string initially assigns during 1st call and changes to nil during 2nd call.

I initially connected the delegates to xib through the storyboard, Then I called the xib class from one view controller, which will eventually be calling the xib init(frame). I wrote the code to load the xib in it's init(frame). Since I already connected the xib with the storyboard, xib will also call it init(coder) method.

so what I did was, removed the delegates from storyboard and called "self.pickerView.delegate" and "self.pickerView.dataSource" in its init(frame), eventually the init(coder) method stop calling.

Now, the value of string is not changing.

Answer 2

Do these checks and see if your code follows the same. delegate is a weak variable.

• As delegate is an optional, make sure you do not force unwrap it. Use ? instead of ! .

• Make sure the Protocol is being implemented by the class that this delegate points to.

• Make sure that delegate variable is assigned with self in the implemented class.

A sample playground demo would be.

class CustomPickerMenu
{
    var statusLabel = String()

    var pickerArray = [String]()
    weak var delegate:Sample?

    func call() {
        pickerArray = ["One", "Two"]
        print(pickerArray)
    }
    func pick()
    {
        statusLabel = pickerArray[0]
        print(statusLabel)
    }

    @IBAction func saveStatus(_ sender: Any)
    {
        print(statusLabel)
        self.delegate?.doSomething(data: statusLabel)
        print(statusLabel)
    }
}

class Apply: Sample {

    func test() {
        let picker = CustomPickerMenu()
        picker.call()
        picker.pick()
        picker.delegate = self
        picker.saveStatus(self)
    }
    func doSomething(data: String) {
        print(data)
    }
}

let apply = Apply()
apply.test()