Rails：从关联模型中获取所有用户

Question

Say I have an article model, user model and comment model. If I want to get all users that commented on a particular article is this the best way or is there a better way?

User.find(Article.first.comments.pluck(:user_id))

Answer 1

You have a few options.

You can add

has_many :users, through: :comments

to Article then just say:

@article.users

If you don't want to do that for some reason you can do

@article.comments.collect(&:user)

I think this would be more efficient:

@article.comments.includes(:users).collect(&:user)

I hope that helps.