按钮的用户默认值

Question

I am brand new here. I´ve been trying to research more info but not success, hopefully someone could help me with this:

I am building an app like a checkbox in one ViewController ( CLViewController ), and what I am using are buttons as an image and once pressed they change its display to another image. (Check/Unchecked -- item1a/item1b)

The app has other ViewControllers where you can have different information, but the problem that I have is the moment I go back to this CLViewController when I´m moving from another ViewControllers, the CLViewController returns to its default value which are all unchecked. My intention is to keep the Checked buttons as they were when i left them. I know how to use userDefaults for texts but I don´t know how to code for buttons and its state.

import UIKit


class CLviewControllerViewController: UIViewController {

    @IBOutlet weak var btn1: UIButton!
    @IBOutlet weak var btn2: UIButton!
    @IBOutlet weak var btn3: UIButton!




    @IBAction func btn1Action(_ sender: UIButton)
    {
        if sender.isSelected == true
        {
            btn1.setImage(UIImage (named: "item1a"), for: .normal)
            sender.isSelected = false
        }
        else
        {
            btn1.setImage(UIImage (named: "item1b"), for: .normal)
            sender.isSelected = true        
          }

Answer 1

First in viewDidLoad we will assign each button with a tag, btn1 will have tag 0, btn2 will have tag 1 and btn3 will have tag 2. Then we can read the value stored in UserDefaults and set the appropriate state. Note that we will store them for key Item- tag so btn3 will be stored as Item-2 . Then in your @IBAction we store the state so that it can be retrieved when you get back to this view controller.

@IBOutlet weak var btn1: UIButton!
@IBOutlet weak var btn2: UIButton!
@IBOutlet weak var btn3: UIButton!


override func viewDidLoad() {
    super.viewDidLoad()

    for (index, btn) in [btn1, btn2, btn3].enumerated() {
        btn?.tag = index

        let selected = UserDefaults.standard.bool(forKey: "Item-\(index)")
        btn?.isSelected = selected
    }

}

@IBAction func btn1Action(_ sender: UIButton)
{
    if sender.isSelected == true
    {
        btn1.setImage(UIImage (named: "item1a"), for: .normal)
        sender.isSelected = false
    }
    else
    {
        btn1.setImage(UIImage (named: "item1b"), for: .normal)
        sender.isSelected = true
    }
    let tag = sender.tag
    //save state
    UserDefaults.standard.set(sender.isSelected, forKey: "Item-\(tag)")
}