Rails关联has_many通过代替HABTM

Question

I'm fairly new to rails and ActiveRecord and I'm trying to find the correct way to model my data.

I am building an application that let's swim instructors put together a class plan that shows what skills they will be teaching their class and what activities they will use to teach each skill. A Plan can contain many Skills and each Skill can have many Activities associated with it.

On the Plan form there is a widget for the skill-activity combination. In it, user should be able to select a Skill from a dropdown and for the selected skill select multiple activities from a list. This widget can repeat any number of times on the form.

My current model:

Class Plan
  has_many :plan_activities
end

Class PlanActivities
  belongs_to :plan
  belongs_to :skill
  has_and_belongs_to_many :activities
end

Class Skill
end

Class Activity
end

Is this model correct? My problem with it is that accepts_nested_attribtues_for does not work for HABTM associations. I've read that I can replace it with has_many through:, but that would mean adding yet another join model to the picture. It just seems a little too ugly. Is there a better way to do this?

EDIT:

My Skills and Activities are in list form and I should be able to include the same skill and/or activity on multiple plans.

Answer 1

Your model is very close. One improvement here would be to completely remove the PlanActivities model. Just have the associations directly on the plan. At this point I don't think the extra model is justified. We have a pretty basic pyramid structure here. At the top is plan with many skills, Each skill has many activities, so a simpler model would look like:

class Plan
  has_many :plan_skills
  has_many :activities, through: :plan_skills
end

class Skill
  has_many :activities, through: plan_skills
  has_many :plan_skills

end

class PlanSkill
  belongs_to :plan
  belongs_to :skill
  has_many :activities
end


class Activity
  belongs_to :plan_skill
end

The join model is an option but not entirely necessary here. Plan.activities will make the needed join table for you.