Add presence of problem to translation

app/controllers/translations_controller.rb

@@ -69,6 +69,6 @@ class TranslationsController < ApplicationController
 
     # Never trust parameters from the scary internet, only allow the white list through.
     def translation_params
-      params.require(:translation).permit(:title, :content)
+      params.require(:translation).permit(:title, :content, :problem_id)
     end
 end

app/models/translation.rb

@@ -1,7 +1,7 @@
 class Translation < ActiveRecord::Base
   belongs_to :problem, inverse_of: :translations
 
-  validates :title, :content, presence: true
+  validates :title, :content, :problem, presence: true
   validates :title, uniqueness: true
 
   self.per_page = 50