如何使用NSUserdefaults保存设置

Question

I am making a tip calculator and the requirement is to have a settings page to go along with the calculator. In the calculator there are three options implemented by a segmented control when each is selected, the value of the tip and the value of the total change. In my settings tab I would like to be able to have the user save their default tip percentage. I know I need to use NSUserdefaults, however I do not know how to do this using two different pages (or one page for that matter). If what I want to achieve is unclear, please let me know I tried my best explaining it thoroughly.

Here is the code for the view controller:

@IBAction func onEditingChanged(sender: AnyObject) {

    var tipPercentages = [0.18, 0.2, 0.22]

    let tipPercentage = tipPercentages[tipControl.selectedSegmentIndex]

    let billAmount = billField.text!._bridgeToObjectiveC().doubleValue

    let billAmt = billAmount

    let tip = billAmt * tipPercentage

    let total = billAmt + tip

    tipLabel.text = String(format:"$%.2f", tip)

    totalLabel.text = String(format:"$%.2f", total)

}

Here is what I have for the settingsViewController:

import UIKit

class SettingsViewController: UIViewController {

@IBOutlet weak var defaultTipControl: UISegmentedControl!



@IBAction func actDefaultTipCont(sender: AnyObject) {

    var tipPercentages = [0.18, 0.2, 0.22]

    var tipPercentage = [defaultTipControl.selectedSegmentIndex]

    let defaults = NSUserDefaults.standardUserDefaults()

    defaults.setObject(tipPercentage, forKey: "tippingDefault")

    defaults.setInteger(123, forKey: "tippingInteger")

    defaults.synchronize()

}

I have just been messing around with the settingsViewController trying to get it to work, it will likely all have to be redone. Here are pictures of the views of the two different pages:

Entry View

Settings Page

Thank you ahead of time for the help!

Answer 1

To save then retrieve the data, you want to do something like this:

let valueToSave = tipAmount;
let defaults = NSUserDefaults.standardUserDefaults()
defaults.setObject(valueToSave, forKey: "tipAmount")

Then to retrieve it and use it on your main control (for example) do this:

let defaults = NSUserDefaults.standardUserDefaults()
tipAmount = defaults.objectForKey("tipAmount")

the valueForKey method returns whatever you saved in that key previously

NSUserdefaults is basically just a dictionary that will persist over different launches, so just check if you have saved a value for a specific key to access it