--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Simoleon/Helpers/Persistence.swift	Tue Oct 12 16:17:35 2021 +0200
@@ -0,0 +1,66 @@
+//
+//  Persistence.swift
+//  Simoleon
+//
+//  Created by Dennis Concepción Martín on 08/07/2021.
+//
+
+import CoreData
+
+struct PersistenceController {
+    static let shared = PersistenceController()
+    
+    static var preview: PersistenceController = {
+        let result = PersistenceController(inMemory: true)
+        let viewContext = result.container.viewContext
+        
+        for _ in 0..<10 {
+            let favoritePair = FavoritePair(context: viewContext)
+            favoritePair.baseSymbol = "USD"
+            favoritePair.quoteSymbol = "EUR"
+        }
+        
+        do {
+            try viewContext.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)")
+        }
+        return result
+    }()
+    
+    let container: NSPersistentCloudKitContainer
+    
+    init(inMemory: Bool = false) {
+        container = NSPersistentCloudKitContainer(name: "Simoleon")
+        container.viewContext.automaticallyMergesChangesFromParent = true
+        container.viewContext.mergePolicy = NSMergeByPropertyStoreTrumpMergePolicy
+        if inMemory {
+            container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
+        }
+        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)")
+            }
+        })
+    }
+}