UserDefaults不将数据保留在TextView中

Question

Edit: I noticed I am using different keys (was playing with the code), but even if they are same, I get similar results.

I have looked all over StackOverflow but not found a solution for this. I have a textview on a second view in my storyboard, and I need it to persist the data without any button press. I should go to the view, see the text and when the app backgrounds (or view disappears), it should persist that data.

I've got it working to the point the text appears on the second view (via a segue), but it doesn't update with new text which is appended via the loop and doesn't persist the data. Also, if I tap a "clear" button to clear the view, it clears the textview but as soon as I go back to the view, the data comes back.

In essence it's stuck on saving just one line of my textview and nothing more. Any help would be appriciated as I am very new to Xcode. (Latest Xcode with Swift 3).

import Foundation
import UIKit

class CalcViewController: UIViewController {
    var tape = Array<String>()

    @IBOutlet weak var calcTape: UITextView!

    override func viewDidLoad() {
        super.viewDidLoad()

        for eachNewLineInTape in tape {
            calcTape.text = calcTape.text + eachNewLineInTape + "\r\n"
        }

        let sel:Selector = #selector(self.appMovedToBackground)
        let notificationCentre = NotificationCenter.default
        notificationCentre.addObserver(self, selector: sel, name: NSNotification.Name.UIApplicationWillResignActive, object: nil)

        let defaults = UserDefaults.standard

        if let userDataNew:AnyObject = defaults.object(forKey: "userDataNew") as AnyObject?{
            calcTape.text = (userDataNew as! Array).first

            print("SAVED")
        }
        else {
            print("not saved")
        }
    }

    @IBAction func clearAll(_ sender: UIButton) {
        // if the tape is not empty...
        if (calcTape.text != ""){
            // empty it (set to empty string)
            calcTape.text = ""
            let bundleIdentifier = Bundle.main.bundleIdentifier
            UserDefaults.standard.removePersistentDomain(forName: bundleIdentifier!)
        } else {
            // otherwise, it was already empty, so display a message
            let alert = UIAlertController(title: "Alert", message: "Nothing to clear", preferredStyle: UIAlertControllerStyle.alert)
            alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
            self.present(alert, animated: true, completion: nil)
        }
    }

    func appMovedToBackground(){
        print("App moved to background")
        let myText = calcTape.text
        UserDefaults.standard.set(myText, forKey: "savedStringKey")
        UserDefaults.standard.synchronize()
        print("saved")
    }
}

Answer 1

I assume that you tested and verified that appMovedToBackground is called.

First, as it was mentioned in the comments, you need to use the same key.

Then, in your saving code:

let myText = calcTape.text
UserDefaults.standard.set(myText, forKey: "savedStringKey")

myText has String type, so it should store it as is.

But then in your loading code, you are doing something really strange. This line should succeed and userDataNew will have your saved string.

if let userDataNew:AnyObject = defaults.object(forKey: "userDataNew") as AnyObject?{

But after that you are force casting it to Array . Your program must crash straight away:

calcTape.text = (userDataNew as! Array).first

The correct way for loading should be just:

calcTape.text = UserDefaults.standard.string(forKey: "savedStringKey")

Slightly off topic, but a few improvements in your code: Instead of this:

for eachNewLineInTape in tape {
   calcTape.text = calcTape.text + eachNewLineInTape + "\r\n"
}

you could write:

calcTape.text = tape.joined(separator: "\r\n")

Answer 2

Sorry for answering my own question (not sure how else to do it and make it clear), but this is how the code looks now:

import Foundation
import UIKit

class ViewControllerTwo: UIViewController {

var tape = Array<String>()

@IBOutlet weak var calcTape: UITextView!



override func viewDidLoad() {
    super.viewDidLoad()

    calcTape.text = tape.joined(separator: "\r\n")

    let sel:Selector = #selector(self.appMovedToBackground)
    let notificationCentre = NotificationCenter.default
    notificationCentre.addObserver(self, selector: sel, name: NSNotification.Name.UIApplicationWillResignActive, object: nil)

    let defaults = UserDefaults.standard

    if let _:AnyObject = defaults.object(forKey: "savedStringKey") as AnyObject?{

        calcTape.text = UserDefaults.standard.string(forKey: "savedStringKey")

        print("SAVED")
    }
    else {
        print("not saved")
    }


}

@IBAction func clearAll(_ sender: UIButton) {

    // if the tape is not empty...
    if (calcTape.text != ""){

        // empty it (set to empty string)

        calcTape.text = ""
        let bundleIdentifier = Bundle.main.bundleIdentifier
        UserDefaults.standard.removePersistentDomain(forName: bundleIdentifier!)


    } else {
        // otherwise, it was already empty, so display a message
        let alert = UIAlertController(title: "Alert", message: "Nothing to clear", preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
        self.present(alert, animated: true, completion: nil)
    }
}


func appMovedToBackground(){
    print("App moved to background")
    let myText = calcTape.text
    UserDefaults.standard.set(myText, forKey: "savedStringKey")
    print("saved in bg")
    }
}