NSKeyedUnarchiver 不会返回数据答案

【问题标题】：NSKeyedUnarchiver won't return dataNSKeyedUnarchiver 不会返回数据
【发布时间】：2016-06-09 22:41:41
【问题描述】：

我正在制作一个跟踪用户锻炼的应用。我有两个自定义类，第一个是 ExerciseModel，它保存锻炼期间执行的每个锻炼的数据，包括名称、组数、次数等。这是我的数据模型：

import UIKit

class ExerciseModel: NSObject, NSCoding
{
// MARK: Properties
var name: String
var sets: Int
var reps: Int
var heartrate: Int?
var type: String?

//MARK: Archiving Paths
static let DocumentsDirectory = NSFileManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first!
static let ArchiveURL = DocumentsDirectory.URLByAppendingPathComponent("exercises")


// MARK: Initialization
init?(name: String, sets: Int, reps: Int, heartrate: Int?, type: String)
{

// MARK: Initlaize stored properties
self.name = name
self.sets = sets
self.reps = reps
self.heartrate = heartrate
self.type = type

super.init()


// Initialization should fail if there is no name or sets is negative
if name.isEmpty || sets < 0
    {
        return nil
    }

}

struct PropertyKey
{
    static let nameKey = "name"
    static let setKey = "sets"
    static let repKey = "reps"
    static let heartrateKey = "heartrate"
    static let typekey = "type"
}


// MARK: NSCoding
func encodeWithCoder(aCoder: NSCoder)
{
    aCoder.encodeObject(name, forKey: PropertyKey.nameKey)
    aCoder.encodeInteger(sets, forKey: PropertyKey.setKey)
    aCoder.encodeInteger(reps, forKey: PropertyKey.repKey)
    aCoder.encodeObject(type, forKey: PropertyKey.typekey)
}

required convenience init?(coder aDecoder: NSCoder)
{
    let name = aDecoder.decodeObjectForKey(PropertyKey.nameKey) as! String
    let sets = aDecoder.decodeIntegerForKey(PropertyKey.setKey)
    let reps = aDecoder.decodeIntegerForKey(PropertyKey.repKey)
    let heartrate = aDecoder.decodeIntegerForKey(PropertyKey.heartrateKey)
    let type = aDecoder.decodeObjectForKey(PropertyKey.typekey) as? String

    // Must call designated initializer
    self.init(name: name, sets: sets, reps: reps, heartrate: heartrate, type: type!)
}

init?(name: String, sets: Int, reps: Int, heartrate: Int, type: String)
{
    // Initialize stored properties.
    self.name = name
    self.sets = sets
    self.reps = reps
    self.heartrate = heartrate
    self.type = type

}


}

我的第二个自定义类称为 WorkoutStorage，这是为了让用户可以保存整个锻炼并在以后检索它们。练习属性是一个练习模型对象数组，如上所述。这是我的 WorkoutStorage 数据模型：

//

import UIKit

@objc(WorkoutStorage)
class WorkoutStorage: NSObject, NSCoding
{
// MARK: Properties
var name: String
var date: NSDate
var exercises: [ExerciseModel]
var maxHR: Int
var avgHR: Int

// MARK: Archiving Paths
static let DocumentsDirectory = NSFileManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first!
static let ArchiveURL = DocumentsDirectory.URLByAppendingPathComponent("storedWorkouts")

// MARK: Initialization
init?(name: String, date: NSDate, exercises: [ExerciseModel], maxHR: Int, avgHR: Int)
{
    //MARK: Initialize Stored Properties
    self.name = name
    self.date = date
    self.exercises = exercises
    self.maxHR = maxHR
    self.avgHR = avgHR

    super.init()

}

struct PropertyKey
{
    static let nameKey = "name"
    static let dateKey = "date"
    static let exercisesKey = "exercises"
    static let maxHRKey = "maxHR"
    static let avgHRKey = "avgHR"
}

// MARK: NSCoding
func encodeWithCoder(aCoder: NSCoder)
{
    aCoder.encodeObject(name, forKey: PropertyKey.nameKey)
    aCoder.encodeObject(date, forKey: PropertyKey.dateKey)
    aCoder.encodeObject(exercises, forKey: PropertyKey.exercisesKey)
    aCoder.encodeInteger(maxHR, forKey: PropertyKey.maxHRKey)
    aCoder.encodeInteger(avgHR, forKey: PropertyKey.avgHRKey)
}

required convenience init?(coder aDecoder: NSCoder)
{
    let name = aDecoder.decodeObjectForKey(PropertyKey.nameKey) as! String
    let date = aDecoder.decodeObjectForKey(PropertyKey.dateKey) as! NSDate
    let exercises = aDecoder.decodeObjectForKey(PropertyKey.exercisesKey) as! [ExerciseModel]
    let maxHR = aDecoder.decodeIntegerForKey(PropertyKey.maxHRKey)
    let avgHR = aDecoder.decodeIntegerForKey(PropertyKey.avgHRKey)

    // Must call designated initializer
    self.init(name: name, date: date, exercises: exercises, maxHR: maxHR, avgHR: avgHR)
}
}

我按照 Apple 的 Persist Data 教程为此设置了 NSKeyedArchiver 和 NSKeyedUnarchiver，但我仍然无法检索我的数据。当我尝试加载锻炼时，我调用以下函数：

func loadStoredWorkouts() -> WorkoutStorage
{
    NSKeyedUnarchiver.setClass(WorkoutStorage.self, forClassName: "WorkoutStorage")
    NSKeyedArchiver.setClassName("WorkoutStorage", forClass: WorkoutStorage.self)

    print("\(WorkoutStorage.ArchiveURL.path!)")

    return NSKeyedUnarchiver.unarchiveObjectWithFile(WorkoutStorage.ArchiveURL.path!) as! WorkoutStorage
}

目前我只能返回一个 WorkoutStorage 对象，但是当我尝试检索包含所有存储的 WorkoutStorage 对象的数组时，我收到一条错误消息：Could not cast value of type 'Workout_Tracker.WorkoutStorage' (0x1000fcc80 ) 到 'NSArray' (0x19f6b2418)。我已经阅读了很多文档，试图弄清楚为什么这只会返回一个对象，并检查了具有类似问题的问题，但无济于事。我最初按照 Apple Persist Data 教程设置我的应用程序来存储和加载我的 ExerciseModel 对象，这似乎完美无缺。我以同样的方式设置了 WorkoutStorage 类，但这里似乎存在问题。

任何帮助将不胜感激！

**编辑* 这是我用来归档 WorkoutStorage 对象的代码：

func saveWorkoutStorageObject(currentWorkout: WorkoutStorage)
    {
        NSKeyedUnarchiver.setClass(WorkoutStorage.self, forClassName: "WorkoutStorage")
        NSKeyedArchiver.setClassName("WorkoutStorage", forClass: WorkoutStorage.self)

    let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(currentWorkout, toFile: WorkoutStorage.ArchiveURL.path!)
    if !isSuccessfulSave
    {
        print("Failed to save exercises")
    }
    if isSuccessfulSave
    {
        print("Successful save of current workout: \(currentWorkout)")
    }
}

用户一次只创建一个锻炼，所以每次完成一个，我将对象传递给上述函数以存档它。

为了取消归档所有对象，我试图按照以下方式做一些事情：

var workouts = [WorkoutStorage]()

override func viewDidLoad()
{
    super.viewDidLoad()

    workouts = loadStoredWorkouts()
}

loadStoredWorkouts() 函数的位置：

 func loadStoredWorkouts() -> [WorkoutStorage]
    {
        NSKeyedUnarchiver.setClass(WorkoutStorage.self, forClassName: "WorkoutStorage")
        NSKeyedArchiver.setClassName("WorkoutStorage", forClass: WorkoutStorage.self)

    print("\(WorkoutStorage.ArchiveURL.path!)")

    return NSKeyedUnarchiver.unarchiveObjectWithFile(WorkoutStorage.ArchiveURL.path!) as! [WorkoutStorage]
}

【问题讨论】：

我注意到的一个小点（这不是您报告的问题的原因）是您的锻炼模型init 应该将type 声明为String?，然后您应该删除当您从解码器 init 调用 init 时，! 来自 type
您能否展示您归档和取消归档WorkoutStorage 对象数组的代码？此外，CoreData 可能是一个更好的选择
@Paulw11 感谢 Paul。我已更新我的问题以显示该信息
您的saveWorkoutStorageObject 仅存档一次锻炼。它不会归档数组，因此您当然不能取消归档数组。如果您希望能够取消归档数组，则需要归档 workouts 数组。每次将某些内容归档到文件时，都会替换文件的内容。它不会附加到末尾。
@Paulw11 我明白了……这是有道理的。因此，如果我要在第一次锻炼中保存一个数组，那么在我保存第二次锻炼之前，我可以加载数组，附加到它然后保存它，从而有效地覆盖数据？我理解正确吗？

标签： ios swift nskeyedarchiver nskeyedunarchiver

【解决方案1】：

您的saveWorkoutStorageObject 仅存档一次锻炼。它不会归档数组，因此您当然不能取消归档数组。

如果您希望能够取消存档数组，则需要存档 workouts 数组。

每次将某些内容归档到文件时，都会替换文件的内容。它不会附加到末尾。

由于NSKeyedArchiver.archiveRootObject 自动存档子对象，您只需存档数组，您的WorkoutStorage 对象将自动存档

func saveWorkouts(workouts:[WorkoutStorage])
{
    let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(workouts, toFile: WorkoutStorage.ArchiveURL.path!)
    if isSuccessfulSave
    {
        print("Successful save of workouts: \(workouts)")
    } else {
        print("Failed to save exercises")
    }
}

【讨论】：