Add check whether problem has a translation

app/controllers/problems_controller.rb

@@ -6,6 +6,9 @@ class ProblemsController < ApplicationController
   end
 
   def show
+    unless @problem.is_translated?
+      render action: "untranslated"
+    end
   end
 
   private

app/models/problem.rb

@@ -5,4 +5,9 @@ class Problem < ActiveRecord::Base
   has_many :translations, inverse_of: :problem
   
   self.per_page = 50
+
+  def is_translated?
+    !!self.translation
+  end
+
 end

app/views/problems/index.html.erb

@@ -13,7 +13,14 @@
   <% @problems.each do |problem| %>
       <tr>
         <td><%= problem.id %></td>
-        <td><%= link_to problem.title, problem %></td>
+        <td>
+          <% if problem.is_translated? %>
+            <%= link_to problem.title, problem %>
+          <% else %>
+            <i>Dieses Problem wurde noch nicht übersetzt.</i>
+          <% end %>
+
+        </td>
       </tr>
   <% end %>
   </tbody>

app/views/problems/untranslated.html.erb

@@ -0,0 +1 @@
+Dieses Problem wurde noch nicht übersetzt.

db/seeds.rb

@@ -9,7 +9,7 @@
 Translation.delete_all
 Problem.delete_all
 
-for i in 1..103 do
+for i in 1..10 do
   translation = Translation.create(
              problem_id: i,
              title: "Problem Nummer #{i}",
@@ -17,3 +17,5 @@ for i in 1..103 do
   )
   Problem.create(id: i, translation: translation)
 end
+
+Problem.create(id: 11)

test/controllers/problems_controller_test.rb

@@ -11,4 +11,9 @@ class ProblemsControllerTest < ActionController::TestCase
     assert_response :success
   end
 
+  test "should get untranslated problem" do
+    get :show, id: 3
+    assert_response :success
+  end
+
 end

test/fixtures/problems.yml

@@ -7,3 +7,7 @@ one:
 two:
   id: 2
   translation_id: <%= ActiveRecord::FixtureSet.identify(:translation_two) %>
+
+three:
+  id: 3
+

test/models/problem_test.rb

@@ -1,7 +1,16 @@
 require 'test_helper'
 
 class ProblemTest < ActiveSupport::TestCase
-  # test "the truth" do
-  #   assert true
-  # end
+  test "should save correct problem" do
+    problem = Problem.new
+    assert problem.save
+  end
+
+  test "is_translated? should return false for missing translation" do
+    assert_not problems(:three).is_translated?
+  end
+
+  test "is_translated? should return true for existing translation" do
+    assert problems(:one).is_translated?
+  end
 end