Question

我有一个表类别，该表类别与任务表具有一对多关系，并且我尝试使用Moor执行联接。

我想返回一个与类别匹配的任务列表的列表。我该怎么办？

      Stream<List<CategoryWithTask>> watchAllCategories() {
        return (select(categories)
              ..orderBy(([
                (c) => OrderingTerm(expression: c.name),
              ])))
            .join([leftOuterJoin(tasks, tasks.categoryId.equalsExp(categories.id))])
            .watch()
            .map((rows) => rows.map(
                  (row) {
                    return CategoryWithTask(
                        category: row.readTable(categories),
                        task: row.readTable(tasks)); // How do I modify this line to return a list of tasks corresponding to a category?
                  },
                ).toList());
      }

Answer 1

在Github上创建问题之后，我设法找到了Flutter Moor的支持。下面是工作代码；

  Stream<List<CategoryWithTasks>> watchAllCategories() {
    return (select(categories)
          ..orderBy(([
            (c) => OrderingTerm(expression: c.name),
          ])))
        .join([leftOuterJoin(tasks, tasks.categoryId.equalsExp(categories.id))])
        .watch()
        .map((rows) {
          final groupedData = <Category, List<Task>>{};

          for (final row in rows) {
            final category = row.readTable(categories);
            final task = row.readTable(tasks);

            final list = groupedData.putIfAbsent(category, () => []);
            if (task != null) list.add(task);
          }

          return [
            for (final entry in groupedData.entries)
              CategoryWithTasks(category: entry.key, tasks: entry.value)
          ];
        });
  }

如何通过一对多联接创建颤动的摩尔关系

1 个答案: