Ios 在Swift中使用NSCoding在分层类中实现数据持久化的最佳实践是什么？

问题：我已经在iOS应用程序中使用NSKeyedArchiver实现了数据持久化，目前它的功能是保存分层数据，但只保存顶级类的数据。如何从任何级别保存整个层次结构

背景：我正在开发一个iOS应用程序，它使用分层类的数据结构，例如学校、教室、学生。基本上，学校类包含教室数组（以及其他属性，如学区、姓名、电话号码等）。教室类包含学生数组（以及其他属性，如教师、房间号等），学生类具有每个学生的属性（例如姓名、年级、课程等）

该应用程序有三个视图控制器，层次结构的每一层各有一个，允许在每一层更改数据：DistrictTableViewController有一个学校对象数组，可以添加/删除数组元素；SchoolTableViewController有一个教室对象数组，可以从教室对象数组中添加/删除元素，ClassroomViewController允许用户添加/删除/编辑学生

我已经使用NSCoding在所有三个类中实现了数据持久化，目前它的功能是在层次结构中保存数据，但我只能从顶级DistrictTableVC（应用程序入口点）保存数据。DistrictTableVC有一个saveSchools（）方法。相反，我希望能够保存来自三个ViewController中任何一个的更改，例如，对学生属性的更改将立即保存学生对象，以及教室中的学生数组和学校中的教室数组

当前的配置是DistrictTableVC将单个学校对象传递给SchoolTableVC，SchoolTableVC将单个教室对象传递给ClassroomVC。我想我应该做的是：

创建一个名为District的新顶级班级，该班级拥有一系列学校，并使用NSCoding

在三个VCs之间传递一个区域对象，而不是单一的低级对象

将saveSchools（）方法从DistrictTableVC移动到新的District类，允许我从三个ViewController中的任意一个调用它 由于我不是专业人士，我想了解：

我走对了吗？或

也许有人知道更好的方法

感谢您的阅读

class DistrictTableViewController: UITableViewController {

    private let reuseIdentifier = "schoolCell"

    var schoolsArray = [School]()

    override func viewDidLoad() {
        super.viewDidLoad()

        self.navBarTitle.title = "Schools"

        // Load saved Schools if they exist, otherwise load sample data
        if let savedSchools = loadSchools() {
            schoolsArray += savedSchools
            print("Loading saved schools")

            // Update all School stats
            updateSchoolListStats()

        } else {
            // Load the sample data
            loadSampleSchools()
            print("Failed to load saved data. Loading sample data...")
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    //MARK: TableView datasource
    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return schoolsArray.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCell(withIdentifier: reuseIdentifier, for: indexPath) as! SchoolTableViewCell

        // Configure the cell...
        let school = schoolsArray[indexPath.row]
        school.calcSchoolStats()

        return cell
    }

    // Override to support conditional editing of the table view.
    override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
        // Return false if you do not want the specified item to be editable.
        return true
    }

    // Override to support editing the table view.
    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == .delete {

            // Delete the row from the data source
            schoolsArray.remove(at: indexPath.row)
            saveSchools()

            tableView.deleteRows(at: [indexPath], with: .fade)

        } else if editingStyle == .insert {
            // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
        }    
    }

    // MARK: - Navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        super.prepare(for: segue, sender: sender)

        // Deselect any selected cells
        for (_, cell) in tableView.visibleCells.enumerated() {
            cell.isSelected = false
        }

        // SchoolTableViewCell pressed: pass the selected school to SchoolsTableViewController
        if (segue.identifier ?? "") == "showSchoolDetail" {
            //guard let schoolsTableViewController = segue.destination as? SchoolsTableViewController else {
            fatalError("Unexpected destination: \(segue.destination)")
            }
            guard let selectedSchoolCell = sender as? SchoolTableViewCell else {
                fatalError("Unexpected sender: \(String(describing: sender))")
            }
            guard let indexPath = tableView.indexPath(for: selectedSchoolCell) else {
                fatalError("The selected SchoolTableViewCell is not being displayed by the table")
            }

            schoolTableViewController.school = schoolsArray[indexPath.row]
        }

        // Add button pressed: show SchoolAttributesViewController
        if addBarButtonItem == sender as? UIBarButtonItem {
            guard segue.destination is SchoolAttributesViewController else {
                fatalError("Unexpected destination: \(segue.destination)")
            }
        }
    }

    @IBAction func unwindToSessionsTableViewController(sender: UIStoryboardSegue) {

        if let sourceViewController = sender.source as? SchoolsTableViewController, let school = sourceViewController.school {

            if let selectedIndexPath = tableView.indexPathForSelectedRow {
                // Update an existing session
                schoolsArray.array[selectedIndexPath.row] = school
                tableView.reloadRows(at: [selectedIndexPath], with: .none)
            } else {
                // Add a new school to the Table View
                schoolsArray.insert(session, at: 0) // Update date source; add new school to the top of the table

                let newIndexPath = IndexPath(row: 0, section: 0)
                tableView.insertRows(at: [newIndexPath], with: .automatic)
                tableView.cellForRow(at: newIndexPath)?.isSelected = true

                tableView.cellForRow(at: newIndexPath)?.selectedBackgroundView = bgColorView
            }
            //updateSessionListStats()
            //sessionsTableView.reloadData()

            saveSchools()
        }
    }

    //MARK: Actions
    private func saveSchools() {
        let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(schoolsArray, toFile: School.ArchiveURL.path)

        if isSuccessfulSave {
            os_log("Schools successfully saved", log: OSLog.default, type: .debug)
        } else {
            os_log("Failed to save schools...", log: OSLog.default, type: .error)
        }
    }
    //MARK: Private Methods
    private func updateSchoolListStats() {
        for (_, school) in schoolsArray.array.enumerated() {
            for (_, classroom) in school.classroomArray.enumerated() {
                classroom.calcStats()
            }
            school.calcSchoolStats()
        }
    }
    private func loadSchools() -> [School]? {
        return NSKeyedUnarchiver.unarchiveObject(withFile: School.ArchiveURL.path) as? [School]
    }

class School: NSObject, NSCoding {

    //MARK: Properties
    var name: String
    var district: String
    var phoneNumber: Int
    var classroomArray = [Classroom]()

    //MARK: Archiving Paths
    static let DocumentsDirectory = FileManager().urls(for: .documentDirectory, in: .userDomainMask).first!
    static let ArchiveURL = DocumentsDirectory.appendingPathComponent("schoolsArray")

    init (name: String = "Default", district: String = "", phoneNumber: Int = -1, classroomArray = [Classroom]()) {
        self.name = name
        self.district = district
        self.phoneNumber = phoneNumber
        self.classroomArray = classroomArray
    }

    func calcSchoolStats() {
    }

    //MARK: NSCoding Protocol
    func encode(with aCoder: NSCoder) {

        aCoder.encode(name, forKey: "name")
        aCoder.encode(district, forKey: "district")
        aCoder.encode(phoneNumber, forKey: "phoneNumber")
        aCoder.encode(classroomArray, forKey: "classroomArray")
    }
    required convenience init?(coder aDecoder: NSCoder) {
        // The name is required. If we cannot decode a name string, the initializer should fail.
        guard let name = aDecoder.decodeObject(forKey: "name") as? String else {
            os_log("Unable to decode the name for a School object.", log: OSLog.default, type: .debug)
            return nil
        }
        let district = aDecoder.decodeObject(forKey: "district") as! String
        let phoneNumber = aDecoder.decodeInteger(forKey: "phoneNumber")
        let classroomArray = aDecoder.decodeObject(forKey: "classroomArray") as! [Classroom]

        // Must call designated initializer.
        self.init(name: name, district: district, phoneNumber: phoneNumber, classroomArray: classroomArray)
    }
}

class Classroom: NSObject, NSCoding {

    //MARK: Properties
    var teacher: String
    var roomNumber: Int
    var studentArray = [Student]()

    //MARK: Archiving Paths
    static let DocumentsDirectory = FileManager().urls(for: .documentDirectory, in: .userDomainMask).first!
    static let ArchiveURL = DocumentsDirectory.appendingPathComponent("classroomsArray")

    init (teacher: String = "", building: Int = -1, studentArray = [Student]()) {
        self.teacher = teacher
        self.roomNumber = roomNumber
        self.studentArray = studentArray
    }

    func calcStats() {
    }

    //MARK: NSCoding Protocol
    func encode(with aCoder: NSCoder) {

        aCoder.encode(teacher, forKey: "teacher")
        aCoder.encode(roomNumber, forKey: "roomNumber")
        aCoder.encode(studentArray, forKey: "studentArray")
    }
    required convenience init?(coder aDecoder: NSCoder) {
        // The teacher is required. If we cannot decode a teacher string, the initializer should fail.
        guard let teacher = aDecoder.decodeObject(forKey: "teacher") as? String else {
            os_log("Unable to decode the teacher for a Classroom object.", log: OSLog.default, type: .debug)
            return nil
        }
        let roomNumber = aDecoder.decodeInteger(forKey: "roomNumber")
        let studentArray = aDecoder.decodeObject(forKey: "studentArray") as! [Student]

        // Must call designated initializer.
        self.init(teacher: teacher, roomNumber: roomNumber, studentArray: studentArray)
    }
}

class Student: NSObject, NSCoding {

    //MARK: Properties
    var first: String
    var last: String
    var grade: Int
    var courses: [String]

    //MARK: Archiving Paths
    static let DocumentsDirectory = FileManager().urls(for: .documentDirectory, in: .userDomainMask).first!
    static let ArchiveURL = DocumentsDirectory.appendingPathComponent("students")

    init (first: String = "", last: String = "", grade: Int = -1, courses = [String]()) {
        self.first = first
        self.last = last
        self.grade = grade
        self.courses = courses
    }

    //MARK: NSCoding Protocol
    func encode(with aCoder: NSCoder) {

        aCoder.encode(first, forKey: "first")
        aCoder.encode(last, forKey: "last")
        aCoder.encode(grade, forKey: "grade")
        aCoder.encode(courses, forKey: "courses")
    }
    required convenience init?(coder aDecoder: NSCoder) {
        // The first name is required. If we cannot decode a first name string, the initializer should fail.
        guard let first = aDecoder.decodeObject(forKey: "first") as? String else {
            os_log("Unable to decode the first name for a Student object.", log: OSLog.default, type: .debug)
            return nil
        }
        let last = aDecoder.decodeObject(forKey: "last") as! String
        let grade = aDecoder.decodeInteger(forKey: "grade")
        let courses = aDecoder.decodeObject(forKey: "courses") as! [String]

        // Must call designated initializer.
        self.init(first: first, last: last, grade: grade, courses: courses)
    }
}

---

开始工作了！现在，每个视图控制器都有一个district对象，可以在修改数据模型时调用district.saveDistrict（）

类别地区：NSObject，NSCoding{

//MARK: Properties
var array: [School]

//MARK: Archiving Paths
static let DocumentsDirectory = FileManager().urls(for: .documentDirectory, in: .userDomainMask).first!
static let ArchiveURL = DocumentsDirectory.appendingPathComponent("District")

init (array: [School] = [School]()) {
    self.array = array
}

//MARK: Actions
func saveDistrict() {
    let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(array, toFile: District.ArchiveURL.path)

    if isSuccessfulSave {
        os_log("Schools array successfully saved", log: OSLog.default, type: .debug)
    } else {
        os_log("Failed to save schools array...", log: OSLog.default, type: .error)
    }
}
func loadSavedDistrict() -> District? {        
    var savedDistrict = District()
    if let districtConst = NSKeyedUnarchiver.unarchiveObject(withFile: District.ArchiveURL.path) as? [School] {
        savedDistrict = District(array: districtConst)
    }
    return savedDistrict
}

//MARK: NSCoding Protocol
func encode(with aCoder: NSCoder) {
    aCoder.encode(array, forKey: "array")
}
required convenience init?(coder aDecoder: NSCoder) {
    // The array is required. If we cannot decode the array, the initializer should fail.
    guard let array = aDecoder.decodeObject(forKey: "array") as? [School] else {
        os_log("Unable to decode the Schools array object.", log: OSLog.default, type: .debug)
        return nil
    }

    // Must call designated initializer.
    self.init(array: array)
}

---

}

让它工作起来了！现在，每个视图控制器都有一个district对象，可以在修改数据模型时调用district.saveDistrict（）

类别地区：NSObject，NSCoding{

//MARK: Properties
var array: [School]

//MARK: Archiving Paths
static let DocumentsDirectory = FileManager().urls(for: .documentDirectory, in: .userDomainMask).first!
static let ArchiveURL = DocumentsDirectory.appendingPathComponent("District")

init (array: [School] = [School]()) {
    self.array = array
}

//MARK: Actions
func saveDistrict() {
    let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(array, toFile: District.ArchiveURL.path)

    if isSuccessfulSave {
        os_log("Schools array successfully saved", log: OSLog.default, type: .debug)
    } else {
        os_log("Failed to save schools array...", log: OSLog.default, type: .error)
    }
}
func loadSavedDistrict() -> District? {        
    var savedDistrict = District()
    if let districtConst = NSKeyedUnarchiver.unarchiveObject(withFile: District.ArchiveURL.path) as? [School] {
        savedDistrict = District(array: districtConst)
    }
    return savedDistrict
}

//MARK: NSCoding Protocol
func encode(with aCoder: NSCoder) {
    aCoder.encode(array, forKey: "array")
}
required convenience init?(coder aDecoder: NSCoder) {
    // The array is required. If we cannot decode the array, the initializer should fail.
    guard let array = aDecoder.decodeObject(forKey: "array") as? [School] else {
        os_log("Unable to decode the Schools array object.", log: OSLog.default, type: .debug)
        return nil
    }

    // Must call designated initializer.
    self.init(array: array)
}

---

}/P>如果你想在本地设备上坚持，你可以考虑使用CordaDATA来保存你的对象。您可以采取的另一种策略是利用Firebase远程存储数据。如果您序列化（编码）顶级对象（区域数组），则无法单独加载/保存嵌套的学校/教室/学生数组。始终必须加载/保存完整的顶级阵列。对于您的问题，另一种方法可能更可取@Adrian提到了CoreData或Firebase。问问自己：应用程序的一个用户（地区/学校/教室/学生）总共有多少个实体（不同类型）。如果总数超过几百个，您肯定应该使用CoreData或第三方数据库解决方案。感谢您的回复！我可能应该在我的原始帖子中提到，我正在努力避免使用CoreData。再说一次，我不是专业人士，但从我在研究（）中看到的情况来看，CoreData需要进行更多的设置工作。不过我会调查Firebase。。。我想远程数据存储在未来的版本中会很好。为了回答卢茨的问题，它非常小，可能不到100。再次感谢！如果你想坚持本地设备，你可以考虑使用CordaDATA来保存你的对象。您可以采取的另一种策略是利用Firebase远程存储数据。如果您序列化（编码）顶级对象（区域数组），则无法单独加载/保存嵌套的学校/教室/学生数组。始终必须加载/保存完整的顶级阵列。对于您的问题，另一种方法可能更可取@Adrian提到了CoreData或Firebase。问问自己：应用程序的一个用户（地区/学校/教室/学生）总共有多少个实体（不同类型）。如果总数超过几百个，您肯定应该使用CoreData或第三方数据库解决方案。感谢您的回复！我可能应该在我的原始帖子中提到，我正在努力避免使用CoreData。再说一次，我不是专业人士，但从我在研究（）中看到的情况来看，CoreData需要进行更多的设置工作。不过我会调查Firebase。。。我想远程数据存储在未来的版本中会很好。为了回答卢茨的问题，它非常小，可能不到100。再次感谢！