Dry your JSON API - What it probably looks like

sample_posts_controller_1.rb

class PostsController < ActionController::Base
  def index
    @user = User.find_by(api_key: request.authorization)
    if !@user
      return render json: {error: 'invalid api key'}, status: :unauthorized
    end
    @posts = @user.posts
    # ... render JSON
  end
  
  def show
    @user = User.find_by(api_key: request.authorization)
    # ... validate user
  end
end