The most codeless way to write Rest API in Flutter (Retrofit + Freezed)

What you get from here? Reduced code and autocomplete from model

First, i have an API https://yourawesomeurl.com/user that returns the following result, so lets make it useable in flutter;

{
    "status": 200,
    "message": "fetch successfully!",
    "data": {
        "name": "Sheldon",
        "age": 12
    }
}

Setting Up

dependencies:
  freezed_annotation: ^0.14.1
  retrofit: ^1.3.4+1
  json_annotation: ^4.0.0
  dio: ^4.0.0-beta7
  equatable: ^2.0.0

dev_dependencies:
  build_runner: ^1.11.5
  freezed: ^0.14.1
  json_serializable: ^4.0.2
  retrofit_generator: ^1.4.1+3

Template

base_response.dart

import 'package:equatable/equatable.dart';
import 'package:json_annotation/json_annotation.dart';

part 'base_response.g.dart';

@JsonSerializable(genericArgumentFactories: true)
class BaseResponse<T> extends Equatable {
  final String status;
  final T data;
  final String message;

  const BaseResponse({
    this.status,
    this.data,
    this.message,
  });

  factory BaseResponse.fromJson(
    Map<String, dynamic> json,
    T Function(Object json) fromJsonT,
  ) {
    return _$BaseResponseFromJson<T>(json, fromJsonT);
  }

  Map<String, dynamic> toJson(
    Map<String, dynamic> Function(T value) toJsonT,
  ) {
    return _$BaseResponseToJson<T>(this, toJsonT);
  }

  @override
  List<Object> get props => [
        status,
        data,
        message,
      ];
}

user_model.dart

import 'package:freezed_annotation/freezed_annotation.dart';
import 'package:json_annotation/json_annotation.dart';
import 'package:flutter/foundation.dart';

part 'user_model.freezed.dart';
part 'user_model.g.dart';

@freezed
class UserModel with _$UserModel {
  const factory UserModel({required String name, required int age}) =
      _UserModel;

  factory UserModel.fromJson(Object? json) =>
      _$UserModelFromJson(json as Map<String, dynamic>);
}

api.dart

import 'package:dio/dio.dart';
import 'package:yourawesomeproject/models/user_model.dart';
import 'package:retrofit/retrofit.dart';

import 'api_response.dart';

part 'api.g.dart';

@RestApi(baseUrl: "https://yourawesomeurl.com")
abstract class RestClient {
  factory RestClient(Dio dio, {String baseUrl}) = _RestClient;

  @GET("/user")
  Future<ApiResponse<UserModel>> getUser();
}

Usage

Run this command to generate all the codes

> flutter pub run build_runner build

void main() async {
  final dio = Dio();
  
  // Optional: Due to self sign cert issue
  (dio.httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate =
      (HttpClient client) {
    client.badCertificateCallback =
        (X509Certificate cert, String host, int port) => true;
    return client;
  };

  final client = RestClient(dio);

  client.getUser().then((it) => print(it.data!.name));

  runApp(MyApp());
}

That's it, it will print out Sheldon