Saving array using NSUserDefaults crashes app

问题

I feel as if I am doing things correctly, but I am getting an error at the end of my data conversion and retrieval. Please see the code below:

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")
        }
    }

I then save and get the data as follows:

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]

When I call print(loadedArray.first) I get the error: NSArray element failed to match the Swift Array Element type

回答1:

Looks like your code should work fine even with some really weird forced casting going on in your decoder method. Try like this:

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")
    }
}

Testing with plist files:

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)
    }
}

来源：https://stackoverflow.com/questions/35052664/saving-array-using-nsuserdefaults-crashes-app