mistakes controllers

controller_mistakes.rb

Use  variables as instance variables when used.
  ----------------------
  beginners declare all the variables in controllers as instances even if it may not be required. 
The problem with instance variables is that if you make a mistake, you won’t get the error message. 
A good practice here is to use one or two instance variables per action

###############
##   WRONG   ##
###############
  
  class API::ArticlesController
   def index
     @articles = Article.all
     render json: @articles, status: 200
   end
  end

###############
##   RIGHT   ##
###############

  class API::ArticlesController
   def index
     articles = Article.all
     render json: articles, status: 200
   end
end

specify the Response in Api controllers:
--------------------------
  
###############
##   WRONG   ##
###############
  
  class API::ArticlesController
    def create
      article = Article.new(article_params)
      
      if article.save
        render json: article
      else
        render json: { errors: article.errors.full_messages }
      end  
    end
  end

###############
##   RIGHT   ##
###############

  class API::ArticlesController
    def create
      article = Article.new(article_params)
      
      if article.save
        render json: article, status: 201
      else
        render json: { errors: article.errors.full_messages }, status: 422
      end  
    end
end

limit Use of instance Variable in Partials:
-------------------
  
###############
##   WRONG   ##
###############
  
  
  = render 'form'

  # _form.html.haml:
  = simple_form_for [:users, @course] do |f|
    - # some form

###############
##   RIGHT   ##
###############

  = render 'form', course: course

  # _form.html.haml:
  = simple_form_for [:users, course] do |f|
- # some form
    
    Always think about the before_action:
    ----------------
      
    ###############
##   WRONG   ##
###############
  
  
  class Users::CourseController
    def update
      if current_user.has_role?(‘trainer’)
        @course = current_user.courses.find(params[:id])

        if @course.save
          redirect_to courses_path
        else
          render :edit
        end
      else
        redirect_to root_path, notice: ‘You are not authorized’
      end
    end
  end

###############
##   RIGHT   ##
###############

  class Users::CourseController
    before_action :ensure_user_has_access
    before_action :find_course

    def update
      if @course.save
        redirect_to courses_path
      else
        render :edit
      end
    end

    private

    def ensure_user_has_access
      unless current_user.has_role?(‘trainer’)
        redirect_to root_path, notice: ‘You are not authorized’
      end 
    end

    def find_course
@course = current_user.courses.find(params[:id])
    end
end
    
    Use helpers to hide code from views:
    --------------------