Swift4.2如何将由"struct“构造的二维数组保存到UserDefautls？

import Foundation

struct MatrixElement: Codable {
    var value: Int
}

struct Matrix: Codable {
    var elements: [[MatrixElement]]
}

let matrix = Matrix(elements: [[MatrixElement(value: 1), MatrixElement(value: 2)], [MatrixElement(value: 3), MatrixElement(value: 4)]])

let encoder = JSONEncoder()
if let encodedData = try? encoder.encode(matrix) {
    // 将编码后的数据保存到UserDefaults
    UserDefaults.standard.set(encodedData, forKey: "matrixKey")
}

if let encodedData = UserDefaults.standard.data(forKey: "matrixKey") {
    let decoder = JSONDecoder()
    if let decodedMatrix = try? decoder.decode(Matrix.self, from: encodedData) {
        // 使用解码后的Matrix实例
        let elements = decodedMatrix.elements
        // ...
    }
}