Edit and update an article

Implement the edit and update methods in the ArticlesController to allow
for editing and updating an existing article in the application using
the edit_article_path (articles/:id/edit) and a form in the created
edit.html.erb view file. Refactor the form shared between the new and
edit actions into a partial that both views render.

* Add edit and update actions to ArticlesController
* Add tests for edit and update in ArticlesControllerTest
* Refactor new and edit form into _form.html.erb partial
* Refactor repeated code in ArticlesControllerTest

Completes Rails Getting Started Guide:
* 7 CRUDit Where CRUDit Is Due
  * 7.4 Updating an Article
    * 7.4.1 Using Partials to Share View Code
    * 7.4.2 Finishing Up

app/controllers/articles_controller.rb

@@ -22,6 +22,20 @@ def create
     end
   end
 
+  def edit
+    @article = Article.find(params[:id])
+  end
+
+  def update
+    @article = Article.find(params[:id])
+
+    if @article.update(article_params)
+      redirect_to @article, notice: "Article was successfully updated."
+    else
+      render :edit, status: :unprocessable_entity
+    end
+  end
+
   private
     def article_params
       params.require(:article).permit(:title, :body)

app/views/articles/_form.html.erb

@@ -0,0 +1,21 @@
+<%= form_with model: article do |form| %>
+  <div>
+    <%= form.label :title %><br>
+    <%= form.text_field :title %>
+    <% article.errors.full_messages_for(:title).each do |message| %>
+      <div class="error"><%= message %></div>
+    <% end %>
+  </div>
+
+  <div>
+    <%= form.label :body %><br>
+    <%= form.text_area :body %><br>
+    <% article.errors.full_messages_for(:body).each do |message| %>
+      <div class="error"><%= message %></div>
+    <% end %>
+  </div>
+
+  <div>
+    <%= form.submit %>
+  </div>
+<% end %>

app/views/articles/edit.html.erb

@@ -0,0 +1,3 @@
+<h1>Edit Article</h1>
+
+<%= render "form", article: @article %>

app/views/articles/new.html.erb

@@ -1,23 +1,3 @@
 <h1>New Article</h1>
 
-<%= form_with model: @article do |form| %>
-  <div>
-    <%= form.label :title %><br>
-    <%= form.text_field :title %>
-    <% @article.errors.full_messages_for(:title).each do |message| %>
-      <div class="error"><%= message %></div>
-    <% end %>
-  </div>
-
-  <div>
-    <%= form.label :body %><br>
-    <%= form.text_area :body %>
-    <% @article.errors.full_messages_for(:body).each do |message| %>
-      <div class="error"><%= message %></div>
-    <% end %>
-  </div>
-
-  <div>
-    <%= form.submit %>
-  </div>
-<% end %>
+<%= render "form", article: @article %>

app/views/articles/show.html.erb

@@ -1,3 +1,7 @@
 <h1><%= @article.title %></h1>
 
 <p><%= @article.body %></p>
+
+<ul>
+  <li><%= link_to "Edit", edit_article_path(@article) %></li>
+</ul>

test/controllers/articles_controller_test.rb

@@ -6,6 +6,8 @@ def setup
     @title_blank = "Title can't be blank"
     @body_blank = "Body can't be blank"
     @body_short = "Body is too short (minimum is 10 characters)"
+    @article_title = "Sleepy Time"
+    @article_body = "I'm asleep: #{'z' * 1000}"
   end
 
   test "should get index" do
@@ -21,6 +23,7 @@ def setup
     assert_response :success
     assert_select 'h1', @article.title
     assert_select 'p', @article.body
+    assert_select 'a', 'Edit'
   end
 
   test "should get new" do
@@ -32,26 +35,20 @@ def setup
   end
 
   test "should create article" do
-    article_title = "Sleepy Time"
-    article_body = "I'm asleep: #{'z' * 1000}"
-
     assert_difference("Article.count") do
       post articles_url, params: {
         article: {
-          title: article_title,
-          body: article_body
+          title: @article_title,
+          body: @article_body
         }
       }
     end
 
-    article = Article.last
-    assert_redirected_to article_path(article)
-    assert_equal article_title, article.title
-    assert_equal article_body, article.body
+    saved_article_assertions(Article.last)
     assert_equal "Article was successfully created.", flash[:notice]
   end
 
-  test "should display errors if validations fail" do
+  test "should display errors if create validations fail" do
     assert_no_difference("Article.count") do
       post articles_url, params: {
         article: {
@@ -62,10 +59,56 @@ def setup
     end
 
     assert_select "h1", "New Article"
+    form_error_assertions
+  end
+
+  test "should get edit" do
+    get edit_article_url(@article)
+    assert_response :success
+    assert_select "h1", "Edit Article"
     assert_select "form"
-    assert_select "div.error", 3
-    assert_select "div.error", @title_blank
-    assert_select "div.error", @body_blank
-    assert_select "div.error", @body_short
+    assert_select "form div", 3
+  end
+
+  test "should update article" do
+    patch article_url(@article), params: {
+      id: @article.id,
+      article: {
+        title: @article_title,
+        body: @article_body
+      }
+    }
+
+    @article.reload
+    saved_article_assertions(@article)
+    assert_equal "Article was successfully updated.", flash[:notice]
   end
+
+  test "should display errors if update validations fail" do
+    patch article_url(@article), params: {
+      id: @article.id,
+      article: {
+        title: "",
+        body: ""
+      }
+    }
+
+    assert_select "h1", "Edit Article"
+    form_error_assertions
+  end
+
+  private
+    def saved_article_assertions(article)
+      assert_redirected_to article_path(article)
+      assert_equal @article_title, article.title
+      assert_equal @article_body, article.body
+    end
+
+    def form_error_assertions
+      assert_select "form"
+      assert_select "div.error", 3
+      assert_select "div.error", @title_blank
+      assert_select "div.error", @body_blank
+      assert_select "div.error", @body_short
+    end
 end