需要将 json 映射到 Swift 中的模型

我有一个从API获得的JSON响应，JSON如下所示

{
    "data": [
        {
            "_id": "63d9d2d57c0cfe791b2b19f6",
            "step": {
                "_id": "step1",
                "status": "STARTED",
                "children": [
                    {
                        "_id": "step2",
                        "status": "NOT_STARTED",
                        "children": [
                            {
                                "_id": "step3",
                                "status": "NOT_STARTED",
                                "children": [
                                    {
                                        "_id": "step3",
                                        "status": "NOT_STARTED"
                                    }
                                ]
                            }
                        ]
                    }
                ]
            },
            "status": "IN_PROGRESS",
            "createdBy": "2700930039"
        }
    ]
}

JSON可以在彼此内部具有多层子对象.我需要将此JSON响应映射到SWIFT中的模型

以下是我为Json创建的模型

struct NestedJsonModel:Decodable {
   var data:[LotData]
}

struct LotData:Decodable {
   var _id: String
   var step: StepDetails
   var status: String
   var createdBy: String
}

struct StepDetails:Decodable {
   var _id: String
   var status: String
   var children: [ChildSteps]
}

struct ChildSteps:Decodable {
   var _id: String
   var status: String
   var children: [StepDetails] //because children contains the same model as Step Details
}

以下是译码代码

let jsonData = data.data(using: .utf8)!
do {
    let decoder = JSONDecoder()
    let tableData = try decoder.decode(NestedJsonModel.self, from: jsonData)
    result = tableData.data
    print("****************")
    print(result!)
    print("****************")
}
catch {
    print (error)
}

但我一直收到这样的错误

keyNotFound(CodingKeys(stringValue: "children", intValue: nil), Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "data", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "step", intValue: nil), CodingKeys(stringValue: "children", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "children", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: \"children\", intValue: nil) (\"children\").", underlyingError: nil))个