



For book updates, follow @jhipster-book on Twitter.



Facets of Ruby by Dave Thomas

You can learn Ruby in 4 hours. This talks isn't to learn Ruby, but rather to show facets of Ruby. Ruby has made programming fun again for Dave. It's also made him more productive.

Languages and tools make a difference

Ruby has variables, methods, but no types in methods. When Dave first started using Ruby, he had a strong typing background - and was terrified of Ruby's un-typed feature. He first thought Ruby was a toy language for hobbyists because of the lack of typing. Now, many years later, he really likes the lack of typing and hardly even has bugs relating to typing. He notes that with Java we store most of our data in Collections - and those are all Objects - so Java is essentially un-typed as well. How often do you get ClassCastExceptions? The rooms concensus is not not a whole lot. To make up for the lack of typing, Ruby developers tend to write a lot more unit tests.

ActiveRecord - Ruby O/R Mapping Library

Ruby on Rails - not a single line of XML. Uses intelligent defaults and allows you to override them. The following creates a wrapper around the "ranks" table.

class Rank < ActiveRecord::Base

The original author of RoR thinks that every database table should be plural, so singular class names map to plural table names. It's even smart enough to change Person to a "people" database table. Apparently it has a bunch of the singular-to-plural mappings for the English language built-in. The key to Rails is clever defaulting - allow you to write a lot less code, but override if you really need to.

ActiveRecord has many lifecyle hooks (17) that you can override. For example, before_save, before_destroy, validate. For example

def before_save
  self.when_added ||=

I wonder if Rails has any support for transactions and specifying propagation behavior on transactions? I asked Dave this question and it sounds like ActiveRecord has a rich support for transactions - and even wraps the "save" method with a transaction by default.

"Ruby is pretty damn good at web applications"

Simple CGI is a common choice. FastCGI and mod_ruby in Apache are other common choices. There are also a number of different web frameworks for Ruby:

  1. Roll-your-own
  2. Templating systems
    1. erb
    2. Amarita
    3. RDoc templates
  3. Iowa - similar to WebObjects
  4. Ruby on Rails

Ruby on Rails - MVC Framework

Contoller - one method per view. Setup context (a.k.a. the model) for views. Views contain "rhtml" - HTML with embedded Ruby. Lots of helper functions. Can access model data (context) setup by Controller. The name of the method in the Controller determines the name of the view file. A "select" method will dispatch to a "select.rhtml" file. The method name to call in a Controller is determined by the URI - for example, /ranks/view calls the "view" method in the RanksController class. Pretty slick! I like the idea of smart defaults - IMO this should be used a lot more in webapps. I'd love to get away from mapping URLs in Struts, Spring and WebWork.

Rails has built-in support for configurable URLs - so you can change query strings to more slash-type URLs. What about things like client-side validation, success messages and sortable/pageable tables? Do those exist in Rails? I asked Dave and he said said they have good support for success messages with a "flash" concept and the post-to-redirect problem is almost non-existant because most controller invocations are redirects. Client-side validation and sortable/pageable tables don't exist in Rails.

Rails has Needles - and IoC framework similar to Pico. However, there's a fair amount of traffic on the mailing list and a lot of Ruby developers think they just don't need IoC. Dave's suggestion is to use Class Injection.

The largest Ruby application is probably Daves - 55,000 lines or code, couple hundred thousand users. There are entire companies who write all all their applications in Ruby. The founder of Rails wrote it so he could write Basecamp - which is only 4500 lines of code.

Good stuff Dave - and definitely a nice overview of Rails. Will I be digging in an using Rails anytime soon? Not this year, I'm going to have some fun with Tapestry and JSF first. Maybe next year.

Posted in NFJS at Nov 12 2004, 06:39:59 PM MST

Post a Comment:
Comments are closed for this entry.