Very Complex Json with same field name - flutter

Question

My colleague is response for backend development, this is one of example of the API response.
I want to know that how can I separate it to the map?
And There have same name, I am very difficult to handle it. JSON to Dart generated code also will have error case by same name.
Is there have any other solution to handle this Json?
{
"formId": 1,
"formTypeId": 2,
"formTemplateId": 1,
"version": 1,
"history": "N",
"refNum": "AGQ/T01/01/A1/QA2/0001",
"dateOfAcceptance": "2020/12/16 14:54:01",
"dateOfReacceptance": "2020/12/16 14:54:01",
"blockId": 242,
"floorId": 1,
"flatId": 98,
"isPublic": "N",
"locationId": 1,
"fromFloorId": 1,
"toFloorId": 2,
"elevationId": 1,
"isNextVendor": "Y",
"isMultipleVendor": "N",
"formStatusId": 1,
"checkResults": 1,
"submissionDate": "2020/12/16 14:54:01",
"submittedBy": "ADMINISTRATOR",
"siteId": "YLTL",
"formDetails": [
{
"formDetailsId": 1,
"formId": 1,
"title": "A. 驗收項目",
"checkType": 1,
"required": "Y",
"parentId": 0,
"orderNum": 1,
"formDetailsOptions": [],
"fromDetails": [
{
"formDetailsId": 3,
"formId": 1,
"title": "Title group",
"checkType": 2,
"required": "Y",
"parentId": 1,
"orderNum": 1,
"formDetailsOptions": [],
"fromDetails": [
{
"formDetailsId": 4,
"formId": 1,
"title": "門編號：",
"checkType": 5,
"required": "Y",
"parentId": 3,
"orderNum": 1,
"answerVal": "A001",
"formDetailsOptions": []
},
{
"formDetailsId": 5,
"formId": 1,
"title": "位置：",
"checkType": 6,
"required": "Y",
"parentId": 3,
"orderNum": 2,
"formDetailsOptions": [
{
"formDetailsOptionsId": 1,
"formDetailsId": 5,
"orderNum": 1,
"optionDesc": "單位大門",
"defectOpts": "N",
"additionOpts": "N",
"selected": "N"
},
{
"formDetailsOptionsId": 2,
"formDetailsId": 5,
"orderNum": 2,
"optionDesc": "廚房門",
"defectOpts": "N",
"additionOpts": "N",
"selected": "N"
},
{
"formDetailsOptionsId": 3,
"formDetailsId": 5,
"orderNum": 3,
"optionDesc": "廁所客廳",
"defectOpts": "N",
"additionOpts": "N",
"selected": "N"
}
]
},
{
"formDetailsId": 6,
"formId": 1,
"title": "假框抆塞：",
"checkType": 4,
"required": "Y",
"parentId": 3,
"orderNum": 3,
"answerVal": "Y",
"formDetailsOptions": []
},
{
"formDetailsId": 7,
"formId": 1,
"title": "門框尺寸：",
"checkType": 4,
"required": "Y",
"parentId": 3,
"orderNum": 4,
"answerVal": "Y",
"formDetailsOptions": []
},
{
"formDetailsId": 8,
"formId": 1,
"title": "門框木料：",
"checkType": 4,
"required": "Y",
"parentId": 3,
"orderNum": 5,
"answerVal": "Y",
"formDetailsOptions": []
},
{
"formDetailsId": 9,
"formId": 1,
"title": "門框接口：",
"checkType": 4,
"required": "Y",
"parentId": 3,
"orderNum": 6,
"answerVal": "Y",
"formDetailsOptions": []
},
{
"formDetailsId": 10,
"formId": 1,
"title": "門框色澤：",
"checkType": 4,
"required": "Y",
"parentId": 3,
"orderNum": 7,
"answerVal": "Y",
"formDetailsOptions": []
},
{
"formDetailsId": 11,
"formId": 1,
"title": "磨耳及蟻油：",
"checkType": 4,
"required": "Y",
"parentId": 3,
"orderNum": 8,
"answerVal": "Y",
"formDetailsOptions": []
},
{
"formDetailsId": 12,
"formId": 1,
"title": "防火膠條：",
"checkType": 4,
"required": "Y",
"parentId": 3,
"orderNum": 9,
"answerVal": "Y",
"formDetailsOptions": []
},
{
"formDetailsId": 13,
"formId": 1,
"title": "平正及穩固：",
"checkType": 4,
"required": "Y",
"parentId": 3,
"orderNum": 10,
"answerVal": "Y",
"formDetailsOptions": []
},
{
"formDetailsId": 14,
"formId": 1,
"title": "備註：",
"checkType": 7,
"required": "N",
"parentId": 3,
"orderNum": 11,
"answerVal": "Test group remark",
"formDetailsOptions": []
}
]
}
]
},
{
"formDetailsId": 2,
"formId": 1,
"title": "B. 要改善位置及詳情備註：",
"checkType": 1,
"required": "Y",
"parentId": 0,
"orderNum": 2,
"answerVal": "Test B remark",
"formDetailsOptions": []
}
],
"formDefects": [
{
"formDefectsId": 1,
"formId": 1,
"defectRemark": "Test Remark",
"followActionId": 1,
"reporterType": 1,
"formDefectsImgs": [
{
"formDefectsImgId": 1,
"formDefectsId": 1,
"imgType": 1,
"filePath": "data/images/1/DEFECT-20201228150623123-2F3F4H.jpg",
"orderNum": 1
}
]
}
],
"formVendors": [
{
"formVendorId": 2,
"formId": 1,
"vendorId": "3954",
"orderNum": 2,
"isNextVendor": "N",
"formVendorImgs": [
{
"formVendorImgId": 1,
"formVendorId": 2,
"filePath": "data/images/1/QUERY-20201228151423123-2FF2V4.png",
"orderNum": 1
}
],
"vendor": {
"vendorId": "3954",
"vendorDesc": "博西華",
"vendorDescDisp": "BSH"
}
}
],
"formNextVendors": [
{
"formVendorId": 1,
"formId": 1,
"vendorId": "3985",
"orderNum": 1,
"isNextVendor": "Y",
"formVendorImgs": [
{
"formVendorImgId": 2,
"formVendorId": 1,
"filePath": "data/images/1/QUERY-20201228151423123-VD5F5H.png",
"orderNum": 2
}
],
"vendor": {
"vendorId": "3985",
"vendorDesc": "瑞基",
"vendorDescDisp": "Zuki"
}
}
]
}

Answer 1

With this kind of complex json i would suggest using dart packages for serialization. For example:
https://pub.dev/packages/json_serializable
or
https://pub.dev/packages/built_value

Answer 2

If you can share Dart models, then use json_serializable package. That would make things easier. But...
...if you have to live with the JSON response that your colleague developed and you cannot share your models that convert from/to Json, one alternative would be to use https://app.quicktype.io/
I entered your JSON response and out came generated Dart code that seems legit, at a first glance at least.
Example from that code generation:
factory ComplexJson.fromJson(Map<String, dynamic> json) => ComplexJson(
formId: json["formId"],
formTypeId: json["formTypeId"],
formTemplateId: json["formTemplateId"],
version: json["version"],
history: historyValues.map[json["history"]],
refNum: json["refNum"],
dateOfAcceptance: json["dateOfAcceptance"],
dateOfReacceptance: json["dateOfReacceptance"],
blockId: json["blockId"],
floorId: json["floorId"],
flatId: json["flatId"],
isPublic: historyValues.map[json["isPublic"]],
locationId: json["locationId"],
fromFloorId: json["fromFloorId"],
toFloorId: json["toFloorId"],
elevationId: json["elevationId"],
isNextVendor: historyValues.map[json["isNextVendor"]],
isMultipleVendor: historyValues.map[json["isMultipleVendor"]],
formStatusId: json["formStatusId"],
checkResults: json["checkResults"],
submissionDate: json["submissionDate"],
submittedBy: json["submittedBy"],
siteId: json["siteId"],
formDetails: List<MDetail>.from(json["formDetails"].map((x) => MDetail.fromJson(x))),
formDefects: List<FormDefect>.from(json["formDefects"].map((x) => FormDefect.fromJson(x))),
formVendors: List<FormVendor>.from(json["formVendors"].map((x) => FormVendor.fromJson(x))),
formNextVendors: List<FormVendor>.from(json["formNextVendors"].map((x) => FormVendor.fromJson(x))),
);