Flutter数据保护插件sealed_writer的使用

Flutter数据保护插件sealed_writer的使用

sealed_writer 插件可以帮助你生成密封类（sealed classes）来更好地管理你的数据结构。以下是如何在 Flutter 中使用 sealed_writer 的完整示例。

添加依赖

首先，在你的 pubspec.yaml 文件中添加 sealed_writer 和 sealed_writer_generator 依赖：

dependencies:
  sealed_writer: ^latest.version

dev_dependencies:
  sealed_writer_generator: ^latest.version

然后运行 flutter pub get 来获取这些依赖。

导入库

接下来，导入 sealed_writer 库：

import 'package:sealed_writer/sealed_writer.dart';

定义密封类

使用 Manifest 类定义你的密封类。例如，我们定义一个表示天气状况的密封类：

void main() {
  final source = Manifest(
    name: 'Weather',
    items: [
      ManifestItem(
        name: 'WeatherSunny',
        shortName: 'sunny',
        equality: ManifestEquality.data,
        fields: [],
      ),
      ManifestItem(
        name: 'WeatherRainy',
        shortName: 'rainy',
        equality: ManifestEquality.data,
        fields: [
          ManifestField(
            name: 'rain',
            type: ManifestType(
              name: 'int',
              isNullable: false,
            ),
          ),
        ],
      ),
    ],
    params: [],
    fields: [],
  );
}

生成源代码

使用 SourceWriter 和 BackwardWriter 生成源代码：

void main() {
  final source = Manifest(
    name: 'Weather',
    items: [
      ManifestItem(
        name: 'WeatherSunny',
        shortName: 'sunny',
        equality: ManifestEquality.data,
        fields: [],
      ),
      ManifestItem(
        name: 'WeatherRainy',
        shortName: 'rainy',
        equality: ManifestEquality.data,
        fields: [
          ManifestField(
            name: 'rain',
            type: ManifestType(
              name: 'int',
              isNullable: false,
            ),
          ),
        ],
      ),
    ],
    params: [],
    fields: [],
  );

  print('==============');
  print('FORWARD WRITER');
  print('==============');

  final forward = SourceWriter(source, referToManifest: false);
  print(forward.write());

  print('===============');
  print('BACKWARD WRITER');
  print('===============');

  final backward = BackwardWriter(source);
  print(backward.write());
}

示例代码解释

定义密封类

在上述代码中，我们定义了一个名为 Weather 的密封类，它包含两个子类：WeatherSunny 和 WeatherRainy。WeatherRainy 类有一个名为 rain 的整型字段。

生成源代码

SourceWriter 和 BackwardWriter 用于生成源代码。SourceWriter 生成前向代码，而 BackwardWriter 生成后向代码。这些代码将帮助你在运行时根据不同的情况执行不同的操作。

输出示例

以下是生成的源代码片段：

abstract class Weather {
  const factory Weather.sunny() = WeatherSunny;
  
  const factory Weather.rainy({required int rain}) = WeatherRainy;

  bool get isSunny => this is WeatherSunny;
  
  WeatherSunny get asSunny => this as WeatherSunny;

  WeatherSunny? get asSunnyOrNull {
    /* ... */
  }

  bool get isRainy => this is WeatherRainy;

  WeatherRainy get asRainy => this as WeatherRainy;

  WeatherRainy? get asRainyOrNull {
    /* ... */
  }

  R when<R extends Object?>({
    required R Function() sunny,
    required R Function(int rain) rainy,
  }) {
    /* ... */
  }

  R maybeWhen<R extends Object?>({
    R Function()? sunny,
    R Function(int rain)? rainy,
    required R Function(Weather weather) orElse,
  }) {
    /* ... */
  }

  R? whenOrNull<R extends Object?>({
    R Function()? sunny,
    R Function(int rain)? rainy,
    R Function(Weather weather)? orElse,
  }) {
    /* ... */
  }

  R map<R extends Object?>({
    required R Function(WeatherSunny sunny) sunny,
    required R Function(WeatherRainy rainy) rainy,
  }) {
    /* ... */
  }

  R maybeMap<R extends Object?>({
    R Function(WeatherSunny sunny)? sunny,
    R Function(WeatherRainy rainy)? rainy,
    required R Function(Weather weather) orElse,
  }) {
    /* ... */
  }

  R? mapOrNull<R extends Object?>({
    R Function(WeatherSunny sunny)? sunny,
    R Function(WeatherRainy rainy)? rainy,
    R Function(Weather weather)? orElse,
  }) {
    /* ... */
  }
}

class WeatherSunny extends Weather {
  const WeatherSunny();
}

class WeatherRainy extends Weather {
  WeatherRainy({required this.rain});
  
  final int rain;

  [@override](/user/override)
  String toString() => 'Weather.rainy(rain: $rain)';
}