fix bug

app/controllers/exercises_controller.rb

@@ -1334,7 +1334,6 @@ class ExercisesController < ApplicationController
   #导出空白试卷
   def export_exercise
     @exercise_questions = @exercise.exercise_questions.includes(:exercise_choices).order("question_number ASC")
-    @request_url = request.base_url
     filename = "#{current_user.real_name}_#{@course.name}_#{@exercise.exercise_name}_#{Time.current.strftime('%Y%m%d%H%M%S')}.pdf"
     stylesheets = "#{Rails.root}/app/templates/exercise_export/exercise_export.css"
     render pdf: 'exercise_export/blank_exercise', filename: filename, stylesheets: stylesheets

app/helpers/application_helper.rb

@@ -336,9 +336,9 @@ module ApplicationHelper
 
   # 导出pdf时，转化markdown为html
   def to_markdown(text)
+    return nil if text.blank?
     request_url = request.base_url
 
-    return nil if text.blank?
     options = {
         :autolink => true,
         :no_intra_emphasis => true,
@@ -350,7 +350,7 @@ module ApplicationHelper
     }
     markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML,options)
     m_t = markdown.render(text)
-    m_t&.include?("src=\"") ? m_t&.gsub("src=\"","src=\"#{request_url}") : m_t
+    m_t&.include?("src=\"") ? m_t&.gsub("src=\"","src=\"#{request.base_url}") : m_t
     Rails.logger.info("###########__________request_url_________###################{request_url}")
   end