fixed back/forward

app/models/post.rb

@@ -69,11 +69,11 @@ class Post < ActiveRecord::Base
   }
 
   def self.next(post)
-    where("posts.created_at > ?", post.created_at)
+    where("posts.created_at > ?", post.created_at).order('posts.created_at ASC').last
   end
 
   def self.previous(post)
-    where("posts.created_at < ?", post.created_at)
+    where("posts.created_at < ?", post.created_at).first
   end
 
   def post_type

app/presenters/post_presenter.rb

@@ -17,7 +17,6 @@ class PostPresenter
     }
   end
 
-
   def next_post_url
     if n = next_post
       Rails.application.routes.url_helpers.post_path(n)
@@ -31,11 +30,11 @@ class PostPresenter
   end
 
   def next_post
-    post_base.next(post).first
+    post_base.next(post)
   end
 
   def previous_post
-    post_base.previous(post).first
+    post_base.previous(post)
   end
 
   protected