根据父模型和子模型的参数获取平均计数

Question

If a User has_many Items . And items can be published by setting the :published attribute in items to true .

How do I get the average number of published items , per user that created an item?

I have a scope for items called published , so you can get all published items by writing:

@items = Item.published
@items = @user.items.published

Answer 1

One way is:

   avg = Item.published.count.to_f / User.count

EDIT:

Try this:

  @published_items = User.joins(:items).where('items.published = ?', true)
  avg = @published_items.count.to_f / @published_items.all(:select => 'distinct users.*').count

Or:

  avg = Item.published.count.to_f / User.joins(:items).where('items.published = ?', true).all(:select => 'distinct users.*').count