ios - 如何创建 Core Data 数据库 swift 4

Question

请分享一些示例代码片段，用于数据库保存详细信息并在 swift 4 中获取保存的详细信息

Answer 1

这是我的答案

第 1 步:创建 Coredata 堆栈类，见下文

var coreDataStack: CoreDataStack = CoreDataStack()//在 appDelegate 上添加这一行

    class Stack
    {
    lazy var managedObjectModel: NSManagedObjectModel = {
    let modelUrl = Bundle.main.url(forResource: "Model", withExtension: "momd")!
    return NSManagedObjectModel(contentsOf: modelUrl)!
}()


lazy var peristentStoreCoordinator: NSPersistentStoreCoordinator = {
    let coordinator: NSPersistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
    let applicationDocumentsDirectory: URL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last!
    let persistentStoreUrl: URL = applicationDocumentsDirectory.appendingPathComponent("Model.sqlite")

    do {
        try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: persistentStoreUrl, options: nil)
    }
    catch {
        fatalError("Persistent store error! \(error)")
    }

    return coordinator
}()


lazy var managedObjectContext: NSManagedObjectContext = {
    let managedObjectContext: NSManagedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
    managedObjectContext.persistentStoreCoordinator = self.peristentStoreCoordinator

    return managedObjectContext
}()


func saveContext() {
    if self.managedObjectContext.hasChanges {
        do {
            try self.managedObjectContext.save()
            }
            catch {
                fatalError("There was an error saving the managed object context \(error)")
            }
        }
    }
}

---

第 2 步:创建实体第 3 步:创建 ManagedObjectModelSubclass -- Editor -> ManagedObjectModelSubclass第 4 步:在类上导入核心数据并添加以下代码

    var person = [Person]() //[Person] here denote subclassclass name
    var  appDelegate = UIApplication.shared.delegate as! AppDelegate

    let personEntity: NSEntityDescription? = NSEntityDescription.entity(forEntityName: "EntityName", in: self.appDelegate.coreDataStack.managedObjectContext)

    if personEntity != nil {

        let person1: Person = Person(entity: personEntity!, insertInto: self.appDelegate.coreDataStack.managedObjectContext)
        person1.name = "name"
        person1.country = "US"
        person1.age = "26"
        person1.place = "NewYork"
     }

第 5 步:使用以下代码获取数据

  var persons: [Person] = [] // subclass name

  var appDelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate

var listdata = [ModelClass]() // create a modelclass object

  func fetchDemoData() {
    let fetchRequest: NSFetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "EntityName")
    do {
        if let results = try self.appDelegate.coreDataStack.managedObjectContext.fetch(fetchRequest) as? [NSManagedObject] {
            let personList: [Person]? = results as? [Person]
            if personList != nil {
                self.persons = personList!


                for eachData in persons {

                    let name = eachData.name as String!
                    let username = eachData.age as String!
                    let email = eachData.country as String!
                    let address = eachData.place as! [String : Any]

                    self.listdata.append(ModelClass(name: name!, username: username!,email : email!,address : address))
                }

                 //self.tableview.reloadData()

            }


        }
    }
    catch {
        fatalError("There was an error fetching the items")
    }
}