Week two half-way point

Hi, please take a look specifically at reviews_controller.rb. I left my original code prior to the solutions in the code intentionally to get some feedback.   Turns out I had forgotten to put the belongs_to :user in my review.rb and thats why my     @review = @video.reviews.build(review_params.merge!(user: current_user))
line would not work. But now I'm thinking that since I have the belongs_to :user,  won't the entire hash of the user be associated with the review just because of the user_id stored in the reviews table?  In case it's not clear, won't my commented lines of code:

    #@review = @video.reviews.build(review_params)
    #@review.user_id = current_user.id
accomplish the same thing as:
    @review = @video.reviews.build(review_params.merge!(user: current_user))

I'm assuming if so, then the true benefit is accomplishing the same thing in one line of code vs two lines of code?
You're seriously telling me that one line method will do everything in the method I created?  lol..

Second thought about this part is that I tried putting my method in the model multiple times, for some reason it was always giving me undefined method average rating, so I gave up and put it in my controller. I even got it working in the controller and copy/pasted it to the model. I'll try again though.