MVP for adding cursor based pagination to an scaffolded Rails blog

cursor-based-pagination-mvp.patch

commit 3babf31134cafb211041202d19fa6f5a9359aed1
Author: Diego Algorta <diego@oboxodo.com>
Date:   Sat Jan 28 15:59:06 2017 -0300

    Add cursor based pagination

diff --git a/app/controllers/posts_controller.rb b/app/controllers/posts_controller.rb
index 16bba99..a921aff 100644
--- a/app/controllers/posts_controller.rb
+++ b/app/controllers/posts_controller.rb
@@ -4,7 +4,9 @@ class PostsController < ApplicationController
   # GET /posts
   # GET /posts.json
   def index
-    @posts = Post.all
+    @posts = Post.paginated
+    @posts = @posts.before(params[:before]) if params[:before]
+    @posts = @posts.after(params[:after]) if params[:after]
   end
 
   # GET /posts/1
diff --git a/app/models/post.rb b/app/models/post.rb
index 791dcb5..817ac44 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -1,2 +1,5 @@
 class Post < ActiveRecord::Base
+  scope :paginated, -> { order(:id).limit(5) }
+  scope :before, -> (id) { paginated.reverse_order.where("posts.id < ?", id).reverse }
+  scope :after, -> (id) { paginated.where("posts.id > ?", id) }
 end
diff --git a/app/views/posts/index.html.erb b/app/views/posts/index.html.erb
index 9985e4f..c757e6f 100644
--- a/app/views/posts/index.html.erb
+++ b/app/views/posts/index.html.erb
@@ -27,3 +27,5 @@
 <br>
 
 <%= link_to 'New Post', new_post_path %>
+<%= link_to 'Prev', posts_path(before: @posts.first) %>
+<%= link_to 'Next', posts_path(after: @posts.last) %>