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

Question

i可以成功保存由" struct"组成的数组，它是[structdata]通过下面使用这些代码。

。

    // save [dataCell] encoded to JSON
    func save(_ cellDatas: [cellData]){
        let encoDatas = cellDatas.map{ try? JSONEncoder().encode($0)}
        UserDefaults.standard.set(encoDatas, forKey: "datas")
    }
    // decode JSON array to [cellData]
    func load() -> [cellData]{
        guard let encodedData = UserDefaults.standard.array(forKey: "datas") as? [Data] else {
            return []
        }
        return encodedData.map{try! JSONDecoder().decode(cellData.self, from: $0)}
    }
    // retrieve datas from UD
    func retrieveData() -> [cellData]{
        datas = UserDefaults.standard.array(forKey: "datas") == nil ? initialData : load()
        return datas
    }

但是，现在我被要求保存一个二维数组，即[[structData]]，以便我尝试了这些代码，替换了一些代码。但这无效。

//     save [dataCell] encoded to JSON
    func saveTableList(_ tableList: [[cellData]]){
        let encoDatas = tableList.map{ try? JSONEncoder().encode($0)}
        UserDefaults.standard.set(encoDatas, forKey: "tableList")
    }
    // decode JSON array to [cellData]
    func loadTableList() -> [[cellData]]{
        guard let encodedData = UserDefaults.standard.array(forKey: "tableList") as? [[Data]] else {
            return []
        }
        return encodedData.map{try! JSONDecoder().decode(cellData.self, from: $0)}
// this $0 has the error that "Cannot convert value of type '[Data]' to expected argument type 'Data'"
//so I tryied this way instead.
//         return encodedData.map{try! JSONDecoder().decode(cellData.self, from: encodedData)}
//but it didn't work properly
    }
    // retrieve datas from UD
    func retrieveTableListData() -> [cellData]{
        datas = UserDefaults.standard.array(forKey: "datas") == nil ? initialData : load()
        return datas
    }

我如何使用UserDefautls ??

Answer 1

为什么不一次编码整个2D数组，而不是创建编码对象的数组。我尝试了一下，它起作用了。

  func saveTableList(_ tableList: [[cellData]]) {
    guard let encodedCellData = try? JSONEncoder().encode(tableList) else {
        print("Error")
        return
    }
    UserDefaults.standard.set(encodedCellData, forKey: "tableList")
}
func loadTableList() -> [[cellData]] {
    guard let encodedCellData = UserDefaults.standard.value(forKey: "tableList") as? Data,
        let cellData = try? JSONDecoder().decode([[cellData]].self, from: encodedCellData) else {
            return []
    }
    return cellData
}