调整

app/models/competition_module.rb

@@ -3,7 +3,7 @@ class CompetitionModule < ApplicationRecord
 
   belongs_to :competition
 
-  has_many :competition_module_md_contents, dependent: :destroy
+  has_one :competition_module_md_content, dependent: :destroy
 
   def module_url
     result_url = url.present? ? url : case module_type

app/models/competition_stage.rb

@@ -5,6 +5,7 @@ class CompetitionStage < ApplicationRecord
   has_many :competition_entries, dependent: :destroy
   has_many :competition_scores, dependent: :destroy
 
+  has_one :competition_module_md_content, dependent: :destroy
   has_one :chart_rule, dependent: :destroy
 
   def min_start_time

app/views/competitions/competition_modules/show.json.jbuilder

@@ -1,7 +1,8 @@
 json.extract! @module, :id, :name, :position, :url
 
-mds = @module.competition_module_md_contents
-json.md_contents mds.each do |md|
+md = @module.competition_module_md_content
+if md.present?
+  json.md_id md.id
   json.md_name md.name
   json.md_content md.content
   json.competition_stage_id md.competition_stage_id