update core data

README.md

@@ -34,6 +34,7 @@
 - [UserDefaults](#UserDefaults)
     - [How to find documentDirectory](#How-to-find-documentDirectory)
 - [Core Data](#Core-Data)
+    - [Set Up Core Data](#Set-Up-Core-Data)
 - [Third Party Library](#Third-Party-Library)
 - [GCD](#GCD)
     - [DispatchQueue](#DispatchQueue)
@@ -491,6 +492,99 @@ let defaults = UserDefaults.standard
 
 > Image From London App Brewery
 
+### Set Up Core Data
+
+Simply Click Core Data check box when you create a new project
+
+<img src = "https://github.com/jphong1111/Useful_Swift/blob/main/Images/DataStoreInSwift.png" width = "50%" height = "50%"/>
+
+If you want to attach Core Data in exsiting project
+
+Create **Data Model** file first
+
+<img src = "https://github.com/jphong1111/Useful_Swift/blob/main/Images/DataStoreInSwift.png" width = "50%" height = "50%"/>
+
+Then import CoreData inside your **AppDelegate.swift** file
+
+```swift
+import CoreData
+```
+
+And Copy and Paste this lines of code inside your **AppDelegate.swift** file
+
+```swift
+    // MARK: - Core Data stack
+
+    lazy var persistentContainer: NSPersistentContainer = {
+        /*
+         The persistent container for the application. This implementation
+         creates and returns a container, having loaded the store for the
+         application to it. This property is optional since there are legitimate
+         error conditions that could cause the creation of the store to fail.
+        */
+        let container = NSPersistentContainer(name: "Your DataModel file name")
+        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
+            if let error = error as NSError? {
+                // Replace this implementation with code to handle the error appropriately.
+                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
+                 
+                /*
+                 Typical reasons for an error here include:
+                 * The parent directory does not exist, cannot be created, or disallows writing.
+                 * The persistent store is not accessible, due to permissions or data protection when the device is locked.
+                 * The device is out of space.
+                 * The store could not be migrated to the current model version.
+                 Check the error message to determine what the actual problem was.
+                 */
+                fatalError("Unresolved error \(error), \(error.userInfo)")
+            }
+        })
+        return container
+    }()
+
+    // MARK: - Core Data Saving support
+
+    func saveContext () {
+        let context = persistentContainer.viewContext
+        if context.hasChanges {
+            do {
+                try context.save()
+            } catch {
+                // Replace this implementation with code to handle the error appropriately.
+                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
+                let nserror = error as NSError
+                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
+            }
+        }
+    }
+```
+
+Don't forget to change it
+```swift
+let container = NSPersistentContainer(name: "Your DataModel file name")
+```
+
+And goto **SceneDelegate.swift** file, copy below lines of code and replace yours
+
+```swift
+func sceneDidEnterBackground(_ scene: UIScene) {
+        // Called as the scene transitions from the foreground to the background.
+        // Use this method to save data, release shared resources, and store enough scene-specific state information
+        // to restore the scene back to its current state.
+
+        // Save changes in the application's managed object context when the application transitions to the background.
+        (UIApplication.shared.delegate as? AppDelegate)?.saveContext()
+    }
+```
+
+If your target is **below iOS13**, put this line of code in side your sceneDidEnterBackground of **AppDelegate.swift** file
+
+```swift
+self.saveContext()
+```
+
+**You are GOOD TO GO**  👏👏👏
+
 ### Various API Site
 - [rapidAPI](https://www.rapidapi.com)