Rails simple form undefined method `model_name' for nil:NilClass

I want to create a simple form to make new reviews for a recipe that has been posted in a cookbook. I render the review form on the recipe show page, but it keeps giving me the same error:

undefined method `model_name' for nil:NilClass

When I do not render the partial new review form at app/views/recipes/show.html.erb, but instead I create the file app/views/reviews/new.html.erb, only then the form works. I do not understand why the form is not working when I try to render it at show recipe page.

Here is my code:

Simple form for:

<%= simple_form_for(@review, url: recipe_reviews_path(@recipe)) do |f| %>
    <%= f.error_notification %>
    <%= f.input :content %>
    <%= f.input :rating %>
    <%= f.button :submit, class: "btn btn-success" %>
<% end %>

Reviews controller:

class ReviewsController < ApplicationController
  def new
    @recipe = recipe.find(params[:recipe_id])
    @review = Review.new(review_params)
  end

  def create
    @recipe = recipe.find(params[:recipe_id])
    @review = Review.new(review_params)
    @review.recipe = @recipe
    if @review.save
      redirect_to recipe_path(@recipe)
    else
      render 'recipe/show'
    end
  end

  private

  def review_params
    params.require(:review).permit(:content, :rating)
  end
end

Recipes controller:

class RecipesController < ApplicationController
  skip_before_action :authenticate_user!
  def index
    @recipes = Recipe.all
  end

  def show
    @recipe = Recipe.find(params[:id])
    @user = User.find(@recipe.user_id)
    @full_name = @recipe.user.first_name + " " + @recipe.user.last_name
  end
end

Recipe show page:

<div class="review">
  <%= render 'review/new' %>

  <% @recipe.reviews.each do |review| %>
      <%= review.content %>
      <%= review.rating %>
  <% end %>
</div>

Routes:

 resources :recipes, only: [:index, :show] do
    resources :reviews, only: [:create]
  end

Models:

class Recipe < ActiveRecord::Base
  belongs_to :user
  has_many :ingredients, dependent: :destroy
  has_many :reviews, dependent: :destroy

  validates :name, :summary, :course, :kitchen, :photo, :description, presence: true
  validates :summary, length: { maximum: 30 }
  mount_uploader :photo, PhotoUploader

  accepts_nested_attributes_for :ingredients, reject_if: :all_blank, allow_destroy: true
end

model review:

class Review < ActiveRecord::Base
  belongs_to :recipe

  validates :content, length: { minimum: 20 }
  validates :rating, presence: true
  validates_numericality_of :rating, :greater_than_or_equal_to => 0, :less_than_or_equal_to => 5
  validates :content, presence: true
end

Can anyone see the problem? Thank you in advance!

Just create a new instance of Review model in the show action of RecipesController

@review = Review.new

That's all. It will work. :)