NSKeyedArchiver不归档我的Codable类

时间:2018-04-21 02:11:53

标签: ios swift4 nskeyedarchiver codable

这是我的Codable类:

class SensorOutput: Codable {

    var timeStamp: Date?

    var gyroX: Double?
    var gyroY: Double?
    var gyroZ: Double?

    var accX: Double?
    var accY: Double?
    var accZ: Double?

    var magX: Double?
    var magY: Double?
    var magZ: Double?

    init() {}
}

在这里,我尝试编写并读取该类的对象来存档:

    let myData = SensorOutput()
    myData.timeStamp = Date()
    myData.gyroX = 0.0
    myData.gyroY = 0.0
    myData.gyroZ = 0.0
    myData.accX = 0.0
    myData.accY = 0.0
    myData.accZ = 0.0
    myData.magX = 0.0
    myData.magY = 0.0
    myData.magZ = 0.0

    NSKeyedArchiver.archiveRootObject(myData, toFile: filePath)

    if let Data = NSKeyedUnarchiver.unarchiveObject(withFile: filePath) as? SensorOutput {
        print (Data)
    }

这会在归档过程中出错: Error screenshot

PS:我以这种方式收到的filePath:

var filePath: String {
    //1 - manager lets you examine contents of a files and folders in your app; creates a directory to where we are saving it
    let manager = FileManager.default
    //2 - this returns an array of urls from our documentDirectory and we take the first path
    let url = manager.urls(for: .documentDirectory, in: .userDomainMask).first
    print("this is the url path in the documentDirectory \(String(describing: url))")
    //3 - creates a new path component and creates a new file called "Data" which is where we will store our Data array.
    return (url!.appendingPathComponent("Data").path)
}

读取/写入适用于Int或Double以及其他受支持的类型,但不适用于我的类型。怎么了?

3 个答案:

答案 0 :(得分:8)

尽管@ matt的答案包含解决问题的基本信息,但如果您是Swift和iOS编程的新手,可能并不明白如何应用这些信息。

您尝试使用NSKeyedArchiver.archiveRootObject(_:toFile:)这是一种类方法,因此您无需创建NSKeyedArchiver的实例。由于encodeEncodable(_:forKey:)是实例方法,而不是类方法,因此您需要创建NSKeyedArchiver的实例才能使用它。您还需要为归档程序创建NSMutableData以附加字节,并且在编码对象后必须调用finishEncoding

    let sensorOutput = SensorOutput()
    sensorOutput.timeStamp = Date()

    let mutableData = NSMutableData()
    let archiver = NSKeyedArchiver(forWritingWith: mutableData)
    try! archiver.encodeEncodable(sensorOutput, forKey: NSKeyedArchiveRootObjectKey)
    archiver.finishEncoding()

    // You can now write mutableData to a file or send it to your server
    // or whatever.

同样,您尝试使用NSKeyedUnarchiver.unarchiveObject(withFile:)这是一种类方法,但您需要使用decodeDecodable(_:forKey:)decodeTopLevelDecodable(_:forKey:)这些是实例方法。因此,您需要读取存档数据并使用它来创建NSKeyedUnarchiver

的实例
// Read in the data from a file or your server or whatever.
// I'll just make an immutable copy of the archived data for this example.
let data = mutableData.copy() as! Data

let unarchiver = NSKeyedUnarchiver(forReadingWith: data)
do {
    if let sensorOutputCopy = try unarchiver.decodeTopLevelDecodable(SensorOutput.self, forKey: NSKeyedArchiveRootObjectKey) {
        print("deserialized sensor output: \(sensorOutputCopy)")
    }
} catch {
    print("unarchiving failure: \(error)")
}

(我更喜欢decodeTopLevelDecodable方法而不是decodeDecodable,因为如果存档损坏,它会抛出Swift错误而不是崩溃。)

答案 1 :(得分:5)

错误消息告诉您SensorOutput需要从NSObject派生。

但是,根本问题是您使用NSKeyedArchiver时出错了。您正在呼叫archiveRootObject,就像这种类型采用NSCoding一样。它没有。它采用Codable。如果您打算使用此类型为Codable的事实,请调用NSKeyedArchiver encodeEncodable(_:forKey:)进行编码,并调用NSKeyedUnarchiver decodeDecodable(_:forKey:)进行解码。

答案 2 :(得分:0)

您使用错误的方式。它采用Codable协议而不是NSCoding协议。 (正如@matt指出的)

您可以这样解决:

let myData = SensorOutput()
let data = try! PropertyListEncoder().encode(myData)
NSKeyedArchiver.archivedData(withRootObject: data)