flutter - 如何通过数据透视表获取标签的相关列表 - Flutter - Moor

Question

我希望能够得到TaskCategory的相关标签列表。标签通过 Taggable 数据透视表与 TaskCategory 相关。

这是预期的：

我有以下表格：

任务类别表

@DataClassName("TaskCategory")
class TaskCategories extends Table {
  IntColumn get id => integer()();

  TextColumn get title => text().nullable()();

  @override
  Set<Column> get primaryKey => {id};
}

任务表：TaskCategory 的子表。

@DataClassName("Task")
class Tasks extends Table {
  IntColumn get id => integer()();

  TextColumn get title => text().nullable()();

  @JsonKey('task_category_id')
  IntColumn get taskCategoryId => integer().nullable()();

  @override
  Set<Column> get primaryKey => {id};
}

标签表：标签可以附加到任何模型，不仅是任务表，这就是为什么这个表中没有定义相关的 id 列。但是与标签表的关系将在可标记（数据透视）表中定义。

@DataClassName("Tag")
class Tags extends Table {
  IntColumn get id => integer()();

  TextColumn get name => text().nullable()();

  @override
  Set<Column> get primaryKey => {id};
}

可标记表：用于标记和任何其他需要附加标记的模型的数据透视表。该表将负责从诸如 Tasks 或 TaskCategories 之类的模型或任何其他需要一些标签的模型中附加或删除标签。

@DataClassName("Taggable")
class Taggables extends Table {
  @JsonKey('tag_id')
  IntColumn get tagId => integer()();

  @JsonKey('taggable_model_id')
  IntColumn get taggableModelId => integer()();  // it can be id of Task or TaskCategory model or any other model id that need to have tag attached to it.

  @JsonKey('taggable_model_type')
  TextColumn get taggableModelType => text()();  // it store the type of model in string e.g 'task' for Task model and 'task_category' for TaskCategory model so that we can get tags for the model based on model's id and type

  @override
  Set<Column> get primaryKey => {tagId, tagableModelId, tagableModelType};
}

这就是我获得 taskCategory 的多个相关任务的方式，以便我可以在同一个位置显示 TaskCategories 及其任务。但我不知道如何也获取taskCategory的多个相关标签。

TaskCategoryWithTasksAndTags

class TaskCategoryWithTasksAndTags {
  TaskCategoryWithTasksAndTags({
    required this.taskCategory,
    required this.tasks,
    required this.tags,
  });

  final TaskCategory taskCategory;
  final List<Task?> tasks;
  final List<Tag?> tags;
}

  Stream<List<TaskCategoryWithTasksAndTags>>
      watchTaskCategoryWithTasksAndTags() {
    final taskCategoriesStream = select(taskCategories).watch()
    final tasksStream = select(tasks).watch();
    final tags = // how to get taskCategories's related tags through taggables pivot table?

    return Rx.combineLatest3(
        taskCategoriesStream, tasksStream, tags, (
      List<TaskCategory> taskCategories,
      List<Task?> taskList,
      List<Tag?> tagList,
    ) {
      return taskCategories.map((taskCategory) {
        final tasks = taskList
            .where(
              (task) =>
                  task?.taskCategoryId ==
                  taskCategory.id,
            )
            .take(6)
            .toList();

        final tags = tagList.where() // need help to get the tags attached/related to the taskCategory

        return TaskCategoryWithTasksAndTags(
          taskCategory: taskCategory,
          tasks: tasks,
          tags: tags,
        );
      }).toList();
    });
  }