ios - NSKeyedArchiver不存档我的Codable类

这是我的Codable类(class):

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以归档:

    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)
    }

这在归档过程中产生了一个错误:
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/写可用于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？

最佳答案

尽管@matt的答案包含解决问题的基本信息，但是如果您不熟悉Swift和iOS编程，如何应用这些信息可能并不明显。

您尝试使用NSKeyedArchiver.archiveRootObject(_:toFile:)(这是一个类方法)，因此不必创建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实例才能使用它。您还需要为存档器创建一个NSMutableData，以将字节追加到该存档器，并且在对对象进行编码后必须调用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:)(这是一个类方法)，但是您需要使用decodeDecodable(_:forKey:)或decodeTopLevelDecodable(_:forKey:)(这是实例方法)。因此，您需要读入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，因为它会引发Swift错误，而不是在存档损坏时崩溃。)

关于ios - NSKeyedArchiver不存档我的Codable类，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/49951731/