Flutter Freezed Method not found

Question

I'm using Freezed to generate data-class on my flutter project.

I did everything exactly like mentioned in the package readme:

import 'package:freezed_annotation/freezed_annotation.dart';

part 'access_token.freezed.dart';

@freezed
class AccessToken with _$AccessToken {
  @JsonSerializable()
  const factory AccessToken(
    @JsonKey(name: 'access_token') String accessToken,
    @JsonKey(name: 'refresh_token') String refreshToken,
  ) = _AccessToken;

  factory AccessToken.fromJson(Map<String, Object?> json) =>
      _$AccessTokenFromJson(json);
}

The build completes successfully.

When I run the app I'm getting:

lib/services/models/access_token.freezed.dart:118:7: Error: Method not found: '_$$_AccessTokenFromJson'. _$$AccessTokenFromJson(json); ^^^^^^^^^^^^^^^^^^^^^^^ lib/services/models/access_token.freezed.dart:157:12: Error: The method '$$AccessTokenToJson' isn't defined for the class '$_AccessToken'.

• '_$AccessToken' is from 'package:tenant_app/services/models/access_token.dart' ('lib/services/models/access_token.dart'). Try correcting the name to the name of an existing method, or defining a method named '$$_AccessTokenToJson'. return _$$_AccessTokenToJson(

Why Freezed didn't generate that function correctly? What am I missing?

Answer 1

You have to add the following part:

part 'access_token.g.dart';

And you don't need the following:

@JsonSerializable()

And make sure you run (using build or watch below):

flutter pub run build_runner build --delete-conflicting-outputs

I took your example and successfully generated everything using:

import 'package:freezed_annotation/freezed_annotation.dart';

part 'access_token.freezed.dart';
part 'access_token.g.dart';

@freezed
class AccessToken with _$AccessToken {
  const factory AccessToken(
    @JsonKey(name: 'access_token') String accessToken,
    @JsonKey(name: 'refresh_token') String refreshToken,
  ) = _AccessToken;

  factory AccessToken.fromJson(Map<String, Object?> json) => _$AccessTokenFromJson(json);
}

Using freezed_annotation: ^2.1.0, freezed: ^2.1.0+1, build_runner: ^2.2.0, json_annotation: ^4.6.0, json_serializable: ^6.3.1 Make sure to check that those are included (according to OP in comment to this answer, packages was missing).

Generated .g.dart file:

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'access_token.dart';

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

_$_AccessToken _$$_AccessTokenFromJson(Map<String, dynamic> json) =>
    _$_AccessToken(
      json['access_token'] as String,
      json['refresh_token'] as String,
    );

Map<String, dynamic> _$$_AccessTokenToJson(_$_AccessToken instance) =>
    <String, dynamic>{
      'access_token': instance.accessToken,
      'refresh_token': instance.refreshToken,
    };