How to convert Response JSON to Object in Flutter?

Don't need to use cast, you can parse directly to a Map

final Map parsed = json.decode(res); 

After you have a map you can use that data to convert into your Object.

final signUp = SignUpResponse.fromJson(parsed);

And if you want to parse an array of objects, you could do something like this:

//assuming this json returns an array of signupresponse objectsfinal List parsedList = json.decode(res); List<SignUpResponse> list = parsedList.map((val) =>  SignUpResponse.fromJson(val)).toList();

The JSON :

    [     {       "id":1,       "name":"Afghanistan",       "iso3":"AFG",       "iso2":"AF",       "phone_code":"93",       "capital":"Kabul",       "currency":"AFN"     },     {       "id":2,       "name":"Aland Islands",       "iso3":"ALA",       "iso2":"AX",       "phone_code":"+358-18",       "capital":"Mariehamn",       "currency":"EUR"       },    ]

The POJO Class :

    class country{       String id;       String name;       String currency;       country({this.id,this.name,this.currency});       factory country.fromJson(Map<String, dynamic> parsedJson){         return country(         id: parsedJson['id'].toString(),         name : parsedJson['name'].toString(),         currency: parsedJson['currency'].toString()          );       }    }

API CALL :

    await http.post("http://calikidsmap.com/test.php").then((response){    var ddd=jsonDecode(response.body);    Country_object_list = (ddd as List)      .map((data) => new country.fromJson(data))      .toList();

Same answer but, what happens when you have nested JsonObjects?Easy:

Given a jsonResponse like this:

{  "id": 1,  "type": 15,  "innerClass": {    "id": 1,    "type": "testing"  }}

This is an example of how the code looks like:

class MainClass {  int id = 0;  int version = 0;  InnerClass innerClass;  MainClass (      this.id,      this.version,      this.innerClass      );  //Create the same factory converter, but using another inner factory 'fromJson' converter//for the inner class object (InnerClass.fromJson(json['inner_class']))  factory MainClass.fromJson(dynamic json) {    return MainClass(        json['id'] as int, // << put your json response keys instead.        json['version'] as int,        InnerClass.fromJson(json['innerClass']) // << this one    );  }

Then, repeat the same strategy but for the inner class object:

class InnerClass {  int id = 0;  String type = 'testing_type';  InnerClass (      this.id,      this.type      );  factory InnerClass.fromJson(dynamic json) {    return InnerClass(        json['id'] as int,        json['type'] as String    );  }}

Finally, you could cosume that, in another part of you project like this:

try {          mainClassDartObject = MainClass.fromJson(response.body);     } catch (e) {          print(e);     }