One problem that seems to face people when they’re attempting to move their applications into production is the best way to manage deployment of their application. This is where tools like capistrano comes in.

Capistrano was written by Jamis Buck of 37signals. In a lot of ways it has become the defacto way to deploy Ruby on Rails applications. It has also had tools like webistrano build on top of it to provide a graphical interface to the command line tool.

To get started, you need to install the capistrano gem:

gem install capistrano

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authentication, capistrano, config, controllers, create, data, Database, deployment, git, github, passenger, Rails, Ruby, Ruby on Rails, server, webserver

I just started building a new Rails application in version 2.3.4. One feature that I thought was particularly handy is the data seeding that is now built into Ruby on Rails.

Before this feature, you would have to do one of two things. You could seed your data in your migrations. The problem with this approach is that it clutters up your migrations, and can make for more brittle migrations. It also may or may not propagate to your test database when you run your tests, meaning that if you’re counting on it, it may not bee there.

Your second option was to create fixtures and a rake task to import the fixture data into your Rails application. The problem with this is the need to create multiple related objects across multiple files to make all of your data match up, which can create maintenance problems.

So, without further ado, here is the solution now included in Rails. You simple create a file at db/seeds.rb and place ActiveRecord create calls in the file. Here’s an example seeds.rb.
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2.3.4, activerecord, create, data, data seeding, Database, fixtures, migration, rake

One of the most powerful aspects of Ruby on Rails are the associations we can create between two classes. It is immensely convenient to be able to call person.posts rather than doing a SQL statement to find all of the posts with a person_id of X.

Sometimes, we have instances where the associations could be with multiple classes. For example, if we have a Page class that can be associated with an HTMLAdvertisement or an ImageAdvertisement. In that case, we really want to be able to call @page.advertisement to get the advertisement. This is where polymorphic associations come in.

Polymorphic associations allow us to associate a single attribute of the class to any number of specified classes. Here are the Page, HtmlAdvertisement, and ImageAdvertisement models:

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activerecord, Database, migration, mixin modules, polymorphic associations, restful routes

Rails Developers do it with Models

I saw a t-shirt at Mountain West RubyConf this year that said “Rails Developers do it with Models.” Of course, they were talking about the classes we use to access the database. In fact, in Ruby on Rails, when you think of your data, you usually think of Models, not the database. The database is more a mechanism for remembering the data when you’re not using it.

Let’s look at one of the files that were generated in Part I. This file is where the model for our blog’s posts are defined.
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activerecord, Database, migration, MySQL, Rails, Ruby on Rails, tutorial

I wrote a quick overview of Rails Metal earlier and started thinking that it would be nice to provide some examples of how you could use it in your Rails application. Here are 9 ways I thought of off the top of my head.

I’ll provide a quick explanation of each one and then post the code as I get each one done.

1. Authentication checking

Many sites have two parts to them. The administrative side—which is protected by an authentication system—and the public side—which anyone can access. If a user must be logged in to access the admin/authenticated part of the site, then why not take advantage of the performance boost Rails Metal gives you and redirect before the Rails even gets loaded.

UPDATE: I just posted the an explanation of how to do Rails Metal Authentication.

2. OpenID checking

Similar to the Authentication checking, you can do a quick check of the user’s authentication status with their OpenID and let them through if they are already authenticated. It’s kind of like a convenient before_filter call on that section of your website.

3. Simple API’s

API’s are extremely simple to implement with Rails Metal. If you have a convenient method on the Model to convert a given instance into the format the API user expects—to_json for example—then you could simply provide a success response with the converted object as the response text.

UPDATE: I just posted the code and explanation on how to do API’s in Rails Metal.

4. Redirecting Affiliate Links

Have you ever built a site that made money from advertising and wished you could send people to http://mydomain.com/hosting for your hosting affiliate? This would be one of the simplest uses of Rails Metal. Check the path and redirect.

UPDATE: I just posted the an explanation of how to do Rails Metal Redirects.

5. Serving Static Content

If you have pages or some other type of content that doesn’t change from one page load to the next and you don’t need the nice templating magic that the Ruby on Rails layouts give you, then this solution is for you. It allows you to make these pages database driven.

UPDATE: I just posted the an explanation of how to serve Static Content and Pages using Rails Metal.

6. Serving Downloads

Regardless of whether the file you’re serving is a file in the filesystem, or has its data stored in the database, all you really need is the file’s mime-type and its content. Then you give a success response with the content type set in the header and the file content in the response text.

7. Tracking Analytics

Rails Metal was designed to be a possible endpoint for your application, meaning that it returns a response and stops execution. However, you can perform some function and then pass the execution on to the remainder of your application. So storing visits to certain paths is a cinch with Rails Metal.

8. Serving Cached Content

Are you caching your content to memcached or the filesystem? For memcached, loading cached content is as easy as loading the memcached client gem and accessing memcached with they key. The rest is caching on the part of your rails application.

9. Triggering Server Side Events (Jobs and Rake Tasks)

Have you ever thought it would be convenient to hit a particular URL and have it kick off a process on your server? Obviously you’d have to secure it, but we can do that with another Rails Metal that checks authentication. (See #1 and #2.)

If you have any other uses that you’re putting Rails Metal to, let us all know in the comments below.

API, authentication, Database, http, layout, rack, Rails, Rails Metal, response, Ruby, security