@Default using non literal const (like Color)

[bounty1342]

Hi,

I run into an issue, trying to give a default value to a Color:

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

import '../../converter/color_converter.dart';

part 'themable.freezed.dart';
part 'themable.g.dart';

@freezed
abstract class Themable with _$Themable {
  const factory Themable({
    @Default(const Color.fromRGBO(0, 0, 0, 0))
    @ColorIntConv() Color backgroundColorRGB,
  }) = _Themable;

  factory Themable.fromJson(Map<String, dynamic> json) =>
      _$ThemableFromJson(json);
}

The json_converter is the following :

class ColorIntConv implements JsonConverter<Color, int> {
  const ColorIntConv();

  @override
  Color fromJson(int json) => Color(json);

  @override
  int toJson(Color object) => object.value;
}

This give the error :

Error with @JsonKey on backgroundColorRGB. defaultValue is Color, it must be a literal.

By removing the @default, it generates fine (themable.g.dart):

_$_Themable _$_$_ThemableFromJson(Map<String, dynamic> json) {
  return _$_Themable(
    backgroundColorRGB:
        const ColorIntConv().fromJson(json['backgroundColorRGB'] as int),
  );
}

Map<String, dynamic> _$_$_ThemableToJson(_$_Themable instance) =>
    <String, dynamic>{
      'backgroundColorRGB':
          const ColorIntConv().toJson(instance.backgroundColorRGB),
    };

So my take is that by handling those both json_converter et default annotation at the same time, it would be possible to handle Color or even custom type, assuming converter is provided.

What do you think ?

This could also help with : #82

[rrousselGit]

The problem is that jsonserializable doesn't like Color as default value

I can't so much for that. It's jsonserializable the problem, not freezed

[bounty1342]

I thing I found a way to achieve it, not the best one, but it should work.

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

import '../../converter/color_converter.dart';

part 'themable.freezed.dart';
part 'themable.g.dart';

@freezed
abstract class Themable with _$Themable {
  const factory Themable({
    @ColorIntConv()
    @Default(ColorIntConv.defaultColor)
    @JsonKey()
        Color backgroundColorRGB,
  }) = _Themable;

  factory Themable.fromJson(Map<String, dynamic> json) =>
      _$ThemableFromJson(json);
}

@default(ColorIntConv.defaultColor) for Freezed.
@jsonkey() override so Freezed won't try to pass the default value.

Change the converter to handle default value if null :

import 'package:flutter/widgets.dart';
import 'package:json_annotation/json_annotation.dart';

class ColorIntConv implements JsonConverter<Color, int> {
  const ColorIntConv();
  static const Color defaultColor = Color.fromRGBO(0, 0, 0, 0);

  @override
  Color fromJson(int json) => json == null ? defaultColor : Color(json);

  @override
  int toJson(Color object) => object == null ? defaultColor : object.value;
}

No the most concise way but at least it works. Should works with #82 too.

I close it then, thanks for pointing me out to jsonserializable. 😃