iOS数据存储 - CoreData



  • Swift版本: 4.0

    使用 CoreData 可以存储一些常用的数据类型,最终是持久化在 SQLite 中。

    • 创建xcdatamodle文件

    New File -> 选择Data Model -> 命名为MyModel

    • 修改AppDelegate.swift,关联persistentContainer
    func applicationWillTerminate(_ application: UIApplication) {
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
        self.saveContext()
    }
    
    // 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: "MyModel")
        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)")
            }
        }
    }
    
    • 增加Entities

    选中MyModel.xcdatamodeld文件 -> Add Entity(命名为Users)-> 增加 Attributes。

    Attribute表:

    Attribute Type
    username String
    age Integer 16
    • 存储数据
    // save
    let appDelegate = UIApplication.shared.delegate as! AppDelegate
    let context = appDelegate.persistentContainer.viewContext
    
    guard let entity = NSEntityDescription.entity(forEntityName: "Users", in: context) else {
        return
    }
    
    let newUser = NSManagedObject(entity: entity, insertInto: context)
    
    newUser.setValue("zzb", forKey: "username")
    newUser.setValue(18, forKey: "age")
    
    do {
        try context.save()
    } catch {
        print("Save data fail")
    }
    
    • 获取数据
    // get
    let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
    
    do {
        let result = try context.fetch(request)
        for data in result {
            if let data = data as? NSManagedObject {
                let userName = data.value(forKey: "username") as? String
                let age = data.value(forKey: "age") as? Int
                
                print("userName = \(String(describing: userName)), age = \(String(describing: age))")
            }
        }
    } catch {
        print("Fetch fail")
    }
    
    • 删除数据
    // remove
    do {
        let result = try context.fetch(request)
        for data in result {
            if let data = data as? NSManagedObject {
                context.delete(data)
            }
        }
    } catch {
        print("Fetch fail")
    }
    

    Demo源码

    https://github.com/CaryZheng/iOSTutorials


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