Question

Building a website (I’m new to web and Scala and Playframework but have a lot of programming experience) and trying to print out parts of my domain model. I have a domain model with Category -> Goal -> Task. Task knows about the Goal and Goal knows about the Category. Now i’d like to print it out like this

Category1
    Goal1
        Activity1
    Goal2
        Activity2
        Activity3

I use Scala and has done this:

    @tasks.groupBy(_.goal).map { case (goal, tasks) =>
    <ul>
        <li>@goal.name</li>
        <ul>
            @tasks.map { task =>
                <li>@task.name</li>
            }
        </ul>
    </ul>
}

So now it is sorted like this:

Goal1
    Activity1
Goal2
    Activity2
    Activity3

But i would also like to sort I by Category, like the first example i showed. Is there a nice way to do this in Scala or should I change my domain model?

Regards, Lina

Answer 1

You can accomplish this by adding another groupBy:

tasks.groupBy(_.goal).groupBy { case (goal, _) => goal.category }

Or, equivalently:

tasks.groupBy(_.goal).groupBy(_._1.category)

This just takes the map you get from your current approach and groups it by the category of its goal keys, giving you a Map[Category, Map[Goal, Seq[Task]]], which you could use like this:

<ul>
  @tasks.groupBy(_.goal).groupBy(_._1.category).map { case (category, goals) =>
    <li>@category.name
      <ul>
        @goals.map { case (goal, tasks) =>
          <li>@goal.name
            <ul>
              @tasks.map { task => <li>@task.name</li> }
            </ul>
          </li>
        }
      </ul>
    </li>
  }
</ul>

Note that I’ve also adjusted your nesting a bit.