NoMethodError working with two models in Rails 4

Question

I have a rating system for real estate agents. I have an agent model and an agent_review model. The rating is stored in the agent_review table, but I need to display the average rating in a view under the agent model and am running into some issue. All code is posted below, please and thank you in advance.

agent model:

has_many :agent_reviews

agent_review model:

belongs_to :agent

agent view:

<h3>Agent Rating: <%= @agent.agent_reviews.rating %> (<%= @agent.agent_reviews.count %>)</h3>

agent controller show method:

def show
    @agent_reviews = AgentReview.all
    @agent = Agent.find_by_slug(params[:id]) || Agent.find(params[:id])

    if @agent.private_profile? && !current_agent&.super_admin?
      redirect_to root_path, notice: "That user has a private profile"
    else
      @favorite_listings =   @agent.liked_listings.available.includes(:neighborhood)
      @agent_listings = @agent.sales_agent_listings.available.visible
      @mate_posts = @agent.liked_mates.order(:when)

      respond_to do |format|
        format.html
        format.json { render json: @agent }
      end
    end
  end

error:

Answer 1

@agent.agent_reviews is an Active Record relationship - there is no 'rating' for that, since it's more than one agent_review object (the fact that it's plural should tell you that).

So if an agent has 6 reviews, with ratings that vary from 1 to 5, you want to show the average of those. You need to add the following to the agent.rb model file:

def average_rating
  if self.agent_reviews.any?
    sum = 0
    self.agent_reviews.each do |agent_review|
      sum += agent_review.rating
    end
    return sum/self.agent_reviews.count
  else
    return nil    # agent has no reviews, don't divide by zero!
  end
end

(that's more verbose than it needs to be, you could condense it with some SQL magic)

And reference that new method in your view:

<h3>Agent Rating: <%= @agent.average_rating %> (<%= @agent.agent_reviews.count %>)</h3>