class Part{ int id; int reportPartID; String code; String name; int quantity; Part({ this.id, this.reportPartID, this.code, this.name, this.quantity = 1, }); Map toJson(){ return { "id": reportPartID ?? 0, "sparePart":{ "id":id, "partNo": code, "partName":name }, "qty":quantity }; } factory Part.fromJson(Map parsedJson,{Map reportJson}){ return Part( id: parsedJson["id"], reportPartID: reportJson != null ? reportJson["id"] : null, code: parsedJson["partNo"], name: parsedJson["partName"], quantity: reportJson != null ? (reportJson["qty"] ?? 1).toInt() : 1, ); } }