Flutter JSON Serialization - Not generating *.g.dart files

I am new to flutter and the objective is to serialise complex JSON objects which contain other smaller objects.

Using the `json_serializable: ^2.0.0` and the `pubspec.yaml` file looks something like this.


dependencies:
intl: ^0.15.7
json_annotation: ^2.0.0
built_value: ^6.7.1
flutter:
sdk: flutter

dev_dependencies:
build_runner: ^1.0.0
json_serializable: ^2.0.0
built_value_generator: ^6.7.1
flutter_test:
sdk: flutter

The `user.dart` look like this

import 'package:json_annotation/json_annotation.dart';

part 'user.g.dart';

@JsonSerializable(nullable: false)
class User {
final String firstName;
final String lastName;
final DateTime dateOfBirth;
User({this.firstName, this.lastName, this.dateOfBirth});
factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
Map<String, dynamic> toJson() => _$UserToJson(this);
}

I have tried `flutter pub run build_runner build` yet the file user.g.dart doesn't get created and I am facing issue with that.

I also have added the `build.yaml` file with following code

targets:
$default:
builders:
built_value_generator|built_value:
generate_for:
- model/*.dart
json_serializable|json_serializable:
generate_for:
- model/*.dart

Can anyone let me know what I am missing here. Thanks

The constructor's argument shouldn't be optional

User({this.firstName, this.lastName, this.dateOfBirth});

They should be obligatory:

User(this.firstName, this.lastName, this.dateOfBirth);

And the part

'user.g.dart';

should be matching the Uppercase User class:

part 'User.g.dart';

The file name, class, and `part 'Book.g.dart';` should all match.

I had this following error

error

[WARNING] json_serializable:json_serializable on lib/day10/models/sentence.dart:
Missing "part 'sentence.g.dart';".

I noticed that I had to change on the model file this `part 'Sentence.g.dart';` to this `part 'sentence.g.dart';` in other words, I had to lowercase it.

try running

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

I got to know that , file has to be saved before running the command
`flutter packages pub run build_runner build`

I know answer seems so simple.

in my case I had to add **hive_generator** package, along with the build_runner package.
If your model class name is for example transaction.dart, then it would be like this-
``` part 'transaction.g.dart' ```
Run the command-
```flutter packages pub run build_runner build``` it will generate the transaction model for you.

adding

json_serializable: ^6.0.0

to dev_dependencies solve it for me

If you are trying to generate .g files by just running the command `flutter packages pub run build_runner build` and you are not getting your desired result then just try:

1. `flutter clean`

2. 'flutter pub cache repair'

3. `flutter packages pub run build_runner build --delete-conflicting-outputs`

4. delete all the gradle temp files

5. then run `flutter pub get`

6. `flutter packages pub run build_runner build`.

Some times we forgot to save the files, please save the file then run the command.

```sh
flutter packages pub run build_runner build
```