UserDefaults are used to store data that you want to keep even if you drop the app.
It's very simple to use.
In the sample code, the initial value is set with userDefaults.register(defaults: ["KEY_LabelText": "Hello"]] at first.
The .register () is very useful and puts the initial value when there is no data corresponding to the specified key.
Then the label reads the value saved by UserDefault and reflects it in the text of the label.
And when the button is pressed, it updates the value of the userdefaults and label.
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| import UIKit | |
| class ViewController: UIViewController { | |
| var label:UILabel! | |
| var leftBtn:UIButton! | |
| var rightBtn:UIButton! | |
| override func viewDidLoad() { | |
| super.viewDidLoad() | |
| let viewWidth = self.view.frame.width | |
| let viewHeight = self.view.frame.height | |
| //値が無い場合、初期値を設定する | |
| //初期値に "KEY_LabelText”というKeyで"Hello"と設定する | |
| //set init value | |
| let userDefaults:UserDefaults = UserDefaults.standard | |
| userDefaults.register(defaults: ["KEY_LabelText": "Hello"]) | |
| //set label | |
| label = UILabel() | |
| label.frame = CGRect(x: 0, y: viewHeight*0.1, width: viewWidth, height: viewHeight*0.2) | |
| //UserDefaultから値を取り出して、labelに貼り付ける。 | |
| label.text = userDefaults.string(forKey: "KEY_LabelText") | |
| label.textAlignment = NSTextAlignment.center | |
| self.view.addSubview(label) | |
| //set left button | |
| leftBtn = UIButton() | |
| leftBtn.frame = CGRect(x: 0, y: viewHeight*0.5, width: viewWidth*0.5, height: viewWidth*0.5) | |
| leftBtn.addTarget(self, action: #selector(leftBtnClicked(sender:)), for: .touchUpInside) | |
| leftBtn.backgroundColor = UIColor.blue | |
| leftBtn.setTitle("Hello", for: UIControlState.normal) | |
| self.view.addSubview(leftBtn) | |
| //set right button | |
| rightBtn = UIButton() | |
| rightBtn.frame = CGRect(x: viewWidth*0.5, y: viewHeight*0.5, width: viewWidth*0.5, height: viewWidth*0.5) | |
| rightBtn.addTarget(self, action: #selector(rightBtnClicked(sender:)), for: .touchUpInside) | |
| rightBtn.backgroundColor = UIColor.red | |
| rightBtn.setTitle("World", for: UIControlState.normal) | |
| self.view.addSubview(rightBtn) | |
| } | |
| @objc func rightBtnClicked(sender: UIButton){ | |
| label.text = "World" | |
| //UserDefaultの"KEY_LabelText"に"World"を登録する | |
| let userDefaults:UserDefaults = UserDefaults.standard | |
| userDefaults.set("World", forKey: "KEY_LabelText") | |
| } | |
| @objc func leftBtnClicked(sender: UIButton){ | |
| label.text = "Hello" | |
| //UserDefaultの"KEY_LabelText"に"Hello"を登録する | |
| let userDefaults:UserDefaults = UserDefaults.standard | |
| userDefaults.set("Hello", forKey: "KEY_LabelText") | |
| } | |
| } |