使用 NSUserDefaults 保存数组会使应用程序崩溃

Question

我觉得我做的事情好像是正确的，但我在数据转换和检索结束时遇到错误。请看下面的代码：

class Task:NSObject, NSCoding {
        var name:String
        var notes:String
        var date:NSDate
        var taskCompleted:Bool

        init(name:String, notes:String,date:NSDate, taskCompleted:Bool){
            self.name = name
            self.notes = notes
            self.date = date
            self.taskCompleted = taskCompleted
        }

        required init(coder decoder: NSCoder){
            self.name = (decoder.decodeObjectForKey("name") as! String?)!
            self.notes = (decoder.decodeObjectForKey("notes") as! String?)!
            self.date = (decoder.decodeObjectForKey("date") as! NSDate?)!
            self.taskCompleted = (decoder.decodeObjectForKey("taskCompleted") as! Bool?)!
        }

        func encodeWithCoder(coder: NSCoder) {
            coder.encodeObject(self.name, forKey: "name")
            coder.encodeObject(self.notes, forKey: "notes")
            coder.encodeObject(self.date, forKey: "date")
            coder.encodeObject(self.taskCompleted, forKey: "taskCompleted")
        }
    }

然后我保存并获取数据如下：

let nowData = NSKeyedArchiver.archivedDataWithRootObject([nowTasks])
let defaults = NSUserDefaults.standardUserDefaults()
defaults.setObject(nowData, forKey: "nowData")

let loadedData = defaults.dataForKey("nowData")
let loadedArray = NSKeyedUnarchiver.unarchiveObjectWithData(loadedData!) as! [Task]

当我调用 print(loadedArray.first) 时出现错误：NSArray 元素无法匹配 Swift 数组元素类型

Answer 1

看起来你的代码应该可以正常工作，即使在你的解码器方法中进行了一些非常奇怪的强制转换。像这样尝试：

class Task: NSObject, NSCoding {
    var name = String()
    var notes = String()
    var date: NSDate
    var taskCompleted: Bool
    init(name: String, notes: String, date: NSDate, taskCompleted: Bool){
        self.name = name
        self.notes = notes
        self.date = date
        self.taskCompleted = taskCompleted
    }
    required init(coder decoder: NSCoder){
        self.name = decoder.decodeObjectForKey("name") as! String
        self.notes = decoder.decodeObjectForKey("notes") as! String
        self.date = decoder.decodeObjectForKey("date") as! NSDate
        self.taskCompleted = decoder.decodeBoolForKey("taskCompleted")
    }
    func encodeWithCoder(coder: NSCoder) {
        coder.encodeObject(name, forKey: "name")
        coder.encodeObject(notes, forKey: "notes")
        coder.encodeObject(date, forKey: "date")
        coder.encodeBool(taskCompleted, forKey: "taskCompleted")
    }
}

使用 plist 文件进行测试：

let task1 = Task(name: "task1", notes: "note a", date: NSDate(), taskCompleted: false)
let task2 = Task(name: "task2", notes: "note b", date: NSDate(), taskCompleted: true)

let documentsDirectory = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first!
let fileURL = documentsDirectory.URLByAppendingPathComponent("data.plist")

if let filePath = fileURL.path {
    NSKeyedArchiver.archiveRootObject([task1,task2], toFile: filePath)
    if let loadedArray = NSKeyedUnarchiver.unarchiveObjectWithFile(filePath) as? [Task] {
        print(loadedArray.count)

        print(loadedArray.first?.name ?? "")
        print(loadedArray.first?.notes ?? "")
        print(loadedArray.first!.date )
        print(loadedArray.first!.taskCompleted)

        print(loadedArray.last?.name ?? "")
        print(loadedArray.last?.notes ?? "")
        print(loadedArray.last!.date )
        print(loadedArray.last!.taskCompleted)
    }
}

使用 NSUserDefaults 保存数组会使应用程序崩溃

Saving array using NSUserDefaults crashes app

ios

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swift

nsuserdefaults

saving-data