How to return results filtered on relations count to a view in RAILS?

Question

Basically, I defined a property on my model which returns true or false depending on values in another table.

What I want is to have my Index action in the controll

Answer 1

Why your code doesn't work?

Project.where(:is_available?)

Here in the where method, you have to pass a hash of arguments OR a string of (SQL) conditions. What you are trying to do here is to select all projects where the method is_available? returns true. The problem is that the method is_available? is a Ruby method (defined in your model). Since it is a Ruby function, you can't call it inside SQL. The where method is expecting SQL conditions, not ruby code.

(Thanks to @benzado for the comment)

---

To fix your problem:

This is what you are looking for, computed only at the db level:

Project.joins(:workers)
       .select('projects.*')
       .group('projects.id')
       .having('COUNT(workers.*) > 2')

This should returns all project having at least 2 workers associated with.

---

How to improve this?

You can make a scope of this query, to use it everywhere easily:

#in your model
class Project < ActiveRecord::Base
  scope :having_more_than_x_workers, lambda do |workers_count|
    joins(:workers).select('projects.*').group('projects.id').having("COUNT(workers.*) > #{workers_count || 0}")
  end

end

To use it, in your controller for example:

#in your controller
def index
   @projects = Project.having_more_than_x_workers(2)
end