[英]Swift Codable with nested json as string
我用于后端调用的服务返回所有这些 json 结构:
{
"status" : "OK",
"payload" : **something**
}
有些东西可以是一个简单的字符串:
{
"status" : "OK",
"payload" : "nothing changed"
}
或嵌套的 json(具有任何属性的任何 json),例如:
{
"status" : "OK",
"payload" : {
"someInt" : 2,
"someString" : "hi",
...
}
}
这是我的结构:
struct GenericResponseModel: Codable {
let status:String?
let payload:String?
}
我想始终将“有效负载”解码为字符串。 因此,在第二种情况下,我希望“GenericResponseModel”的有效负载属性包含该字段的 json 字符串,但是如果我尝试解码该响应,则会收到错误消息:
Type 'String' mismatch: Expected to decode String but found a dictionary instead
可以存档我想要的吗?
非常感谢
这个怎么样…
声明一个PayloadType
协议......
protocol PayloadType: Decodable { }
并使String
和struct Payload
符合它......
extension String: PayloadType { }
struct Payload: Decodable, PayloadType {
let someInt: Int
let someString: String
}
然后使GenericResponseModel
泛型......
struct GenericResponseModel<T: PayloadType>: Decodable {
let status: String
let payload: T
enum CodingKeys: CodingKey {
case status, payload
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
status = try container.decode(String.self, forKey: .status)
payload = try container.decode(T.self, forKey: .payload)
}
}
然后你可以解码如下...
let data = """
{
"status" : "OK",
"payload" : "nothing changed"
}
""".data(using: .utf8)!
print(try JSONDecoder().decode(GenericResponseModel<String>.self, from: data))
// GenericResponseModel<String>(status: "OK", payload: "nothing changed")
和
let data2 = """
{
"status" : "OK",
"payload" : {
"someInt" : 2,
"someString" : "hi"
}
}
""".data(using: .utf8)!
print(try JSONDecoder().decode(GenericResponseModel<Payload>.self, from: data2))
// GenericResponseModel<Payload>(status: "OK", payload: Payload(someInt: 2, someString: "hi"))
当然,这取决于您事先了解payload
类型。 如果有效负载类型错误,您可以通过抛出特定错误来解决此问题……
enum GenericResponseModelError: Error {
case wrongPayloadType
}
进而…
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
status = try container.decode(String.self, forKey: .status)
do {
payload = try container.decode(T.self, forKey: .payload)
} catch {
throw GenericResponseModelError.wrongPayloadType
}
}
然后在解码时处理这个错误......
let data = """
{
"status" : "OK",
"payload" : {
"someInt" : 2,
"someString" : "hi"
}
}
""".data(using: .utf8)!
do {
let response = try JSONDecoder().decode(GenericResponseModel<String>.self, from: data) // Throws
print(response)
} catch let error as GenericResponseModelError where error == .wrongPayloadType {
let response = try JSONDecoder().decode(GenericResponseModel<Payload>.self, from: data2) // Success!
print(response)
}
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