My .irbrc file

Here's my .irbrc file. This is based off of this post by Thoughtbot about using wirble with your IRB.



This gives me auto-completion, history, color, Rails SQL output and a few other conveniences.

On the Rails merger with Merb

I think overall it will be a good thing.

There obviously are a lot of common goals between the two frameworks but I'm more interested in how they merge some of the more controversial differences. Both teams have already mentioned modularity and internal APIs as something that Rails is going to adopt, but what about some of the smaller differences?
Some of the more difficult issues to be resolved might be:

• Merb's requirement for an explicit call to render or display - will that be optional?
• Merb's mailer and exception handling - Merb way is probably superior
• Rails' extensive use of monkey patching and magic versus Merb's preference for code simplicity
• Rails' use of test/unit versus Merb's RSpec preference - will all of rails internal tests be rewritten in RSpec?
• slices versus engines - support both??
  

None of these issues are huge and insurmountable but there are a lot of differences that will have to be debated. Will it be a full or partial buy-in to the Merb philosophy by the Rails team? If it is a full buy-in, Rails backward compatibility will probably suffer. If Rails 3.0 is only a partial merge of the Merb way, merbists may look at Rails 3.0 as a watered-down bastardization of Merb and just continue using Merb 1.x.

I'm certainly looking forward to seeing what they come up with!

Writing User Stories with Merb, Cucumber, merb_cucumber and webrat

I decided to try out cucumber and webrat for writing user stories in my sample merb application. Merbbit is a merb-based web app for community-driven link submission. Think Digg, Reddit etc.

I had used user stories before but I found so time-consuming as to be of little use. I was hoping that using webrat's shortcuts, the new improved story runner Cucumber and factory_girl would speed up writing these tests.

Getting setup was quite pain-free.

sudo gem install cucumber webrat david-merb_cucumber --no-ri --no-rdoc
merb-gen cucumber --session-type=webrat

This will also install a sample login feature that should pass if you’re using merb-auth. I was using merb-auth but when I ran:

rake features

The feature failed with the error:

Could not find field labeled "login"

This was because I had changed the login field in the login form from 'login' to 'email'. This was easy to fix. In features/login.feature I just changed

And I fill in "login" with "i_dont_exist"

to

And I filled in "email" with "i_dont_exist"

And it worked!

One of the first cool things I notice about cucumber is how much more colourful it is than the original user stories. It also discreetly tells you what line and what file the step starts on. This can be useful when you forget which file you wrote the matching step in.

And I fill in "password" with "and_i_dont_have_a_password"  # features/steps/common_webrat.rb:16

The failed login scenario of the Login feature comes for free. I now needed to write a successful login scenario.

Scenario: Successful Login
Given I am not authenticated
And an user exists with login "me@example.com" and password "secret_password"
When I go to /login
And I fill in "email" with "me@example.com"
And I fill in "password" with "secret_password"
And I press "Log In"
Then the login request should succeed
And I should see "me" in user_login

I had to write some new steps before I could run this scenario.

For the step "And a user with login "me", email "me@example.com" and password "secret_password"" I needed to create a step that would populate the database with a user. I decided to use factory girl

$ sudo gem install thoughtbot-factory_girl

add require 'factories' to features/env.rb

features/factories.rb:
gem 'thoughtbot-factory_girl'
require 'factory_girl'

Factory.define :user do |u|
u.login 'me'
u.email 'me@example.com'
u.password 'password'
u.password_confirmation 'password'
u.active 'active'
end

require 'features/steps/common_factory_steps'

features/steps/common_factory_steps:
Given /^a user with login "(.+)", email "(.+)" and password "(.+)"$/ do |login, email, password|
Factory(:user, :login => login, :email => email, :password => password, :password_confirmation => password)
end

For the step "Then the login request should succeed", merb_cucumber comes with a "Then the login request should fail" but not a succeed step. It's easy to create one though.

Then /^the (.*) ?request should succeed/ do |_|
response.should be_successful
end

I can't see an easy way using merb to tell if a specific template has been rendered like in rails integration testing (render_template) so I settled for just verifying that the users login "me" appears inside an element called 'user_login'.

Then /^I should see "(.+)" in (.+)$/ do |message, id|
response.should have_xpath("//*[@id=\"#{id}\" and text()=\"#{message}\"]")
end

This step could be used to test for any piece of text inside an element with a given id.

Sources that helped:
http://github.com/david/merb_cucumber/tree/master
http://github.com/brynary/webrat/tree/master
http://rubybling.blogspot.com/2008/10/merbcucumber-almost-baked.html

Emacs Cheat Sheet

I have been trying to learn emacs. Note the use of the word learn. It's not just something you can just use, you have to learn and get used to a heap of things before you can meaningful use it. There are lots of cheatsheets for emacs out there but I want to compile my own one with just the stuff that is most important to me.

The best way to learn emacs is probably by going through a tutorial like this one and the built-in tutorial but what's missing is a quickstart tutorial for emacs...

Here's my attempt:

C-x Ctrl and press x
M-x Meta/Alt key and press x
C-x y Ctrl and press x and then press y
M-x y Meta/Alt key and press x and then press y

Getting Started

Installing on Debian/Ubuntu: sudo apt-get install emacs

Starting a new file (from the commandline):
emacs filename

Starting a new file (from inside Emacs):
C-x b and type the name of your new file

C-h t - start the builtin tutorial
C-g Abort a command

Saving
C-x C-s Save
C-x s Save all (or a few at a time)

Navigation
C-a Beginning of line
C-e End of line
M-f Forward one word
M-b Backward one word

Editing

C-d == DELETE, deletes character to the right
backspace == Deleting, deletes character to the left
M-d Delete word
C-k Delete to the end of the line
C-x u or C-_ Undo (Redo is more complicated)

Cutting, Copying and Pasting
While copying is still copying, what I think 90% of people know as cutting and pasting is not called as such in Emacs. We have Killing and Yanking. Basically kill == cut, yank == paste. (The name yank is a bit counter-intuitive at first I think. It made me assume it was cut. like you were yanking it out of the text, but in fact you're yanking it back into the text.) Emacs also has the concept of a kill-ring. That's just a fancy name for a clipboard.

C-k Kill/Cut to the end of the line
C-SPACEBAR - mark the start of a piece of text followed one one of the following:
M-w Copy
C-w Kill/Cut

C-y Paste (yank)


Find/Replace

C-s Find... (Search) - This does some cool highlighting of matches
C-s C-s Find again
M-% Replace
C-g Abort


Moving between buffers (fancy name for an open file)

C-x b switch-to-buffer. Prompts for a buffer name and switches the buffer of the current window to that buffer.
C-x C-b list-buffers.
C-x k kill-buffer.

Navigating between open windows (split views and stuff)
C-x o other-window. Switch to another window, making it the active window.

C-x 1 delete-other-windows. Deletes all other windows except the current one, making one window on the screen.

C-x 0 delete-window. Deletes just the current window
C-x 2 split-window-vertically
C-x 3 split-window-horizontally

Exiting
C-x C-c - exit, prompts for saves
C-x C-z - suspend


Thats all for now!



MERB: Rendering JPEG's from actions

While working on my MERB app, I wanted to pull an image from the database and render it inline as if it were a static jpg. I knew how to do this in Rails but not in MERB. It turns out to be really easy, although quite different from how it is done in Rails.

This blog post was very useful to figuring it out.

Let's suppose you have a database model Image and an Images controller and action 'show'. Firstly at the end of your merb_init.rb file, put the following line:

Merb.add_mime_type(:jpg, :to_jpg, %w[image/jpeg], {})

then in the controller add a provides parameter for jpg and

In your model add a method to_jpg like so.

def to_jpeg
  data
end

Where data is the name of the column in your images table that holds the binary data.

Make sure you restart your server after all these changes.

Next your controller should look something like this:

class Image < Application
  provides :xml, :js, :yaml, :jpg

  def show
    image = Image.find(params[:id])
    render image
  end
end

And thats it! If you go to /images/1.jpg (assuming RESTful routing...), the controller will retrieve the image with id 1 and MERB will call the to_jpg method on that object. It will then output that binary image data and send with the correct http header Content-Type parameter.

Merb Gotchas

I'm gonna to keep this post up to date with any gotchas or "mistakes of understanding" that I make as I work on MERB.

First up. Controllers are called the same as models! Example:

$ script/generate controller monkey
Started merb_init.rb ...
Loading Application...
Compiling routes..
Loaded DEVELOPMENT Environment...
      exists  app/controllers
      create  app/controllers/monkey.rb

and

$ script/generate model monkey
Started merb_init.rb ...
Loading Application...
Compiling routes..
Loaded DEVELOPMENT Environment...
  exists  app/models
  create  app/models/monkey.rb

So if you create a controller for monkeys and a model for monkeys, the two class names will both be called Monkey, except one will inherit from controller and the other from model.

In fairness to MERB the generators do warn you about this.

"The name 'Monkey' is reserved."

But it doesn't explain why it is reserved and maybe I'm just thick but it stumped me for longer than it should have.

You never have a chance to make that mistake in Rails because controllers are always like "MonkeyController". (I don't know why merb didn't follow suit... DRYer? simpler?)

What I did to get around that was to make the controller plural. monkeys.rb

Enabling Sessions in MERB

Sessions are disabled by default in MERB (because it makes the performance numbers look great! ;) ). To enable sessions, just set the variable :session_store: in merb.yml to one of activerecord, sequel, datamapper, memory, cookie or mem_cache.

Because I want to use memory for my development sessions and mem_cache for my production environment, I set up config/environments/development.yml and put in:

:session_store: memory
:memory_session_ttl: 3600

and config/environments/production.yml and put in:

:session_store: mem_cache

If you're using memcached with MERB, you need to put

require 'memcache'
CACHE = MemCache.new('127.0.0.1:11211', { :namespace => 'my_app' })

in your merb_init.rb (http://merb.rubyforge.org/classes/Merb/MemCacheSession.html)

HTTP Authentication for MERB

I've just started working on a new web application. It's going to be quite a simple app but speed and responsiveness is important so I decided to try Merb. I'm going to blog about some of the difficulties and (hopefully) solutions I discover as I go through the process. One of the main problems with MERB is the lack of documentation so hopefully with these blog posts, I can help with that.

First up, HTTP authentication. In the merb.yml it says the following:

# If you want to protect some or all of your app with  HTTP basic auth then
# uncomment the following and fill in your credentials you want it to use.
# You will then need to set a 'before' filter in a controller.  For example:
#   before :basic_authentication
#:basic_auth:
#  :username: ezra
#  :password: password
#  :domain: localhost

All well and good, but what if you want to validate the authentication against a database of users?

Well the answer is to overwrite the authenticated? method in BasicAuthenticationMixin

This is easy to do, in your application.rb, do something like this:

class Application < Merb::Controller
 before :basic_authentication

 private
   def authenticated?
     # if you want get the username and password that was inputted via http use:
     # username, password = *credentials
     # then validate the user by authenticating against a datbase or whatever
     # make sure the return value is true or false
   end
end

Note: You still have to uncomment the basic_auth configuration in merb.yml. But it doesn't matter what the username/password is there since you'll be overriding them anyways.