Question

I have a model Enrollment which validates the uniqueness for each course by user:

validates_uniqueness_of :user_id, :scope => :course_id

I created a scope in the Enrollment model where I can pass in the course to narrow down the course by user:

scope :course, lambda { |course| where(:course_id => course.id) }   

By doing this, I can call:

current_user.enrollments.course(@course)

However, it then makes me loop through the result, even though there is only one result (unique course for each user). This is fine, but it seems like there should be a way to simply do the scope and then just access the record without need to loop through one result.

Any ideas? I feel like I’m missing something.

Answer 1

Try this:

current_user.enrollments.course(@course).first

That will generate SQL query with LIMIT 1 statement and return the model directly without wrapping it into an array.

Small note about your scope. As your Enrollment model has course association (has_one :course I assume) you’d better give your scope different name like by_course to prevent collision with course association that allows you to fetch course for a given enrollment.