Swift

Question

我发现这个扩展使用 Codable 保存到 NSUserDefaults

extension UserDefaults {
    func decode<T : Codable>(for type : T.Type, using key : String) -> T? {
        let defaults = UserDefaults.standard
        guard let data = defaults.object(forKey: key) as? Data else {return nil}
        let decodedObject = try? PropertyListDecoder().decode(type, from: data)
        return decodedObject
    }

    func encode<T : Codable>(for type : T, using key : String) {
        let defaults = UserDefaults.standard
        let encodedData = try? PropertyListEncoder().encode(type)
        defaults.set(encodedData, forKey: key)
        defaults.synchronize()
    }
}

但据我所知，我有一个错误 Type 'OfflineRequest' does not conform to protocol 'Decodable' 看起来是因为 Any。

我有下一个要保存的结构：

struct OfflineRequest: Codable {
    let url: String
    let params: [String: Any]
}

这个想法是持久存储由于任何连接问题而失败的请求堆栈（数组）。所以我有 Core Data 数据模型，并且在将其发送到服务器之前将其属性转换为 [String: Any]。但现在我想创建离线优先算法。因此，如果用户离线，我想持久存储 url 和 [String: Any] 参数。这种情况下如何正确处理does not conform to protocol 'Decodable'？

Answer 1

你因为 [String:Any] 而出错我建议你使用 JSONSerialization.data

将 [String:Any] 转换为 Data

然后你可以像这样使用

struct OfflineRequest: Codable {
    let url: String
    let params: Data


    enum CodingKeys: String, CodingKey {
        case url
        case params

    }

    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        params = try values.decode(Data.self, forKey: .params)
        url = try values.decode(String.self, forKey: .url)
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(url, forKey: .url)
        try container.encode(params, forKey: .params)
    }
}

Answer 2

您可以使用 JSONSerialization.data(withJSONObject: Any) 对字典进行编码，并使用 JSONSerialization.JSONObject(with: Data) 对其进行解码。你只需要确保你传递了一个有效的 json 对象（在本例中是一个字典），如果你传递一个类型如 Date 的字典，它将崩溃。像这样尝试：

struct OfflineRequest: Codable {
    let url: String
    let params: [String: Any]
}

extension OfflineRequest {
    init(from decoder: Decoder) throws {
        var container = try decoder.unkeyedContainer()
        url = try container.decode(String.self)
        params = try JSONSerialization.jsonObject(with: container.decode(Data.self)) as? [String:Any] ?? [:]
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.unkeyedContainer()
        try container.encode(url)
        try container.encode(JSONSerialization.data(withJSONObject: params))
    }
}

let test = [OfflineRequest(url: "http://www.google.com", params: ["a":"1","b":"test", "c":["d":"test"]])]

let data = try! JSONEncoder().encode(test)
let loaded = try! JSONDecoder().decode([OfflineRequest].self, from: data)
print(loaded) // [__lldb_expr_3.OfflineRequest(url: "http://www.google.com", params: ["b": test, "a": 1, "c": {\n    d = test;\n}])]\n"

Swift - 将 [String: Any] 的数组保存到 NSUserDefaults

Swift - Save array of [String: Any] to NSUserDefauls

nsuserdefaults

ios

codable

decodable