AppDelegateに処理を任せる

クラス一つ一つに同じ処理を書くのは冗長なので、デリゲートを利用する。

AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
...
  func getValue(key: String) -> String {
    if key == "key1" {
      return "value1"
    } else if key == "key2" {
      return "value2"
    }
    return ""
  }
}

FirstViewController.swift

import UIKit

class FirstViewController: UIViewController {
  let myDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
...
  override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    let value = myDelegate.getValue("key1")
  }
}

SecondViewController.swift

import UIKit

class SecondViewController: UIViewController {
  let myDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
...
  override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    let value = myDelegate.getValue("key2")
  }
}