Merb The Super Bike Of Frameworks

work.rowanhick.com

The Pocket Rocket
Framework

Wednesday, June 11, 2008

Discussion tonight
• Intended for people who don’t know what
Merb is
• Good grasp of Rails concepts
• Not patient enough to google/irc/blog
search etc to get started on Merb
• Touch on a lot of features
• All links/references up on
http://work.rowanhick.com tomorrow

About me

• Product Development Mgr for a startup in Toronto

• Full time with Rails for 2.5 years

• Previously PHP/MySQL for 4 years

• 6 years Prior QA/BA/PM for Enterprise CAD/
CAM software dev company


Objects of Desire

• What are these doing in a presentation
about Ruby web frameworks ?


Bikes vs Cars
• The Porsche, you just open the door, turn the key,
and drive. It has a/c, a stereo, plush upholstery,
everything. Accidents can and do happen but few
and far between, but pretty user friendly.

• The sports bike, it's raw, unadulterated. You can't
hop on it wrapped in cotton wool, way easier to
get burned. However it's faster, easier to replace,
modify and tune things at a lower cost.


Parallels to the world of MVC?

Rails is...
• Very user friendly & well documented
• suitable for 80% most web projects
• a turn-key frame work.


...and

Merb is...
• aiming for that other 20%
• fast as all hell
• going to require a little more skill to get up
and running with
• “the framework for hackers”

Same same but
different
• It’s actually quite similar! (workﬂow, layout)
• However ... don’t start emailing merb
groups asking for feature XYZ to be
implemented “like it is in Rails”
• Don’t expect your app to port without
code changes to Merb (although you’d be
suprised how little needs to change)


Who Built it
• Ezra Zygmuntowicz
• Yehuda Katz
• + many others
• You could get some glory too ..
• http://gweezlebur.com/2008/2/1/so-you-
want-to-contribute-to-merb-core-part-1


Key Philosophy

• All you need and none you
don’t
• No code is faster than no
code


Anything that slows Merb
down is a bug
(my personal favourite)


Merb-core -more gems

• What the ? Isn’t it just Merb ?
• merb-core is the basic slimmed down bare
minimum code
• merb-more contains niceities to help you
along your way (action-args, assets, builder,
cache, freezer, gen, haml, jquery, mailer,
parts, slices)


Switzerland

• Merb is the Switzerland of Ruby
frameworks
• Doesn’t care that you might favour
Datamapper over ActiveRecord
• Lets you choose ORM, Test Framework, JS
Framework, Rack Adaptor


Getting started
• To start off with get both core and more
• gem install merb-core merb-more
• choose your ORM
‣ gem install merb-activerecord
‣ gem install sequel
‣ gem sources -a http://gems.datamapper.org && sudo gem install
addressable english rspec data_objects do_mysql do_postgres do_sqlite3
dm-core dm-more


merb-gen

• Your new friend
• generates code/files for your app
rowan$ merb-gen app speeddemon
RubiGen::Scripts::Generate
create log
create app
...etc

• merb-gen app yourapp --flat (or) --very-flat
puts your application on a serious diet.


Differences
RAILS MERB
Routes config/routes.rb config/router.rb
Initialization config/environment.rb config/init.rb
Environment specific config/environments/* config/environments/*
Plugins vendor/plugins gems
Migrations db/migrate schema/migrations
Testing test test (or) spec
Public public public
Models app/models app/models
Controllers app/controllers app/controllers
Helpers app/helpers app/helpers
Lib lib/ (config in init.rb)


vendor/plugins gems
• Everything is a gem
• Freeze your gems with your app
• gem install -i somegem ~/yourapp/gems/ --
no-ri --no-rdoc
• convert rails plugins, start with merb-gen
plugin plugin_name
• Lots underway http://github.com/search?
q=merb

edit conﬁg/init.rb
• Choose your ORM
use_orm: activerecord
use_test: rspec

• Include dependencies (eg mailer)
dependencies quot;merb_helpersquot;, “merb-parts”
Merb::BootLoader.after_app_loads do
# Add dependencies here that must load after the
application loads:
dependencies quot;merb-mailerquot;
# dependency quot;magic_adminquot; # this gem uses the
app's model classes
end


I want my database.yml
• Patience. Because you’ve told merb you want
active record, just ﬁre merb for the ﬁrst
time:
rowan-laptop:speeddemon rowan$ merb
~ Loaded DEVELOPMENT Environment...
~ loading gem 'merb_activerecord' ...
~ loading gem 'activerecord' ...
~ No database.yml file found in /Users/rowan/testing/speeddemon/
config.
~ A sample file was created called database.sample.yml for you to copy
and edit.

• Copy, edit and save.

merb-gen generators
• Let’s you know what you can create
automagically:
rowan-laptop:b2b_merb rowan$ merb-gen generators

.....

Installed Generators

Rubygems: authenticated, controller, database_sessions_migration,
migration, model, part_controller, resource, resource_controller

• see more http://rubigen.rubyforge.org/


merb-gen model
mymodel
• Synonymous with script/generate mymodel
• Extra points:
✓ dependent on ORM - creates migration or
not
✓ dependent on test framework - creates
spec or unit test


Setup your ﬁrst REST
resource

• merb-gen again
$ merb-gen resource Product title:string

• Sets up controller, views, model, test code
• Get coding!


Controller code
• Looks reasonably similar:
class Products < Application
before :check_access_level
provides :xml

def index
@products = Product.find(:all, :order => :sort_order )
display @products
end

def show
@product = Product.find_by_product_id(params[:id])
raise NotFound unless @product
display @product
end
...


Key Differences
RAILS MERB
products_controller products

redirect_to( hash ) redirect ( string )

respond_to provides / only_provides / display

before/after_ﬁlter before/after

except exclude

render(hash) render or render(‘hello world’)
*optional *mandatory to get a view
logger merb.logger

url_for url


display
• Display handles mime type response
provides :xml
def index
@product = Product.find(params[:id])
display @product
end

• Goto http://127.0.0.1:4000/product/2.xml

• Display then looks for index.xml.erb, if not found
then calls @product.to_xml


Syntactic sugar

• Making controller methods look more like methods
def my_action(id)
product = Product.find(id)
end

• Automagically assigns id from params[:id]

• In merb-more (merb-action-args)


Part Controllers

• Reusable 'components' for use in your views

• Not accessible from outside world, but can see
params hash

• Their own generator

• Again in merb-more (merb-parts)


Implementing Parts
• In conﬁg/init.rb
dependency 'merb-parts'

• Use merb-gen to set it up for you
$ merb-gen part_controller widget
...
create app/helpers/widget_part_helper.rb
create app/parts/widget_part.rb
create app/parts/views/widget_part/index.html.erb

• Edit action(s) then call it from a view
<%= WidgetPart => :index %>


Exceptions
• Handled in app/controllers/exceptions.rb
def show
@product = Product.find_by_product_id(params[:id])
raise NotFound unless @product
display @product
end

• exceptions.not_found method

• render out in that view what you want to show for
that error


Router is Powerful
• Example from Yehudas slides at RailsConf


Pressing the GO button

• Simple
merb -p 3000 -e development

• Fires up a mongrel instance through merb

• Hit it just like regular old rails app


Hooking up to
webserver
• Merb implements a Rack adaptor

• Allows you to use different types of application
server depending on your needs

• Example
merb -p 3000 -e production -a thin

• Mongrel, Thin, Ebb, Eventd Mongrel, Passenger

• Connect Apache/Nginx -> Merb (not) Apache ->
Mongrel -> Merb


Resources
http://merbivore.com Great videos
http://wiki.merbivore.com http://mwrc2008.confreaks.com/

http://merbunity.com
http://www.slideshare.net/search/
http://merborials.com/
slideshow?q=merb

http://www.slideshare.net/search/
http://github.com/search?q=merb
slideshow?q=datamapper


The million dollar
question

Should I use it ?


How long is a piece of
string !


work.rowanhick.com

The End


Credits
• GT3 Pic - http://flickr.com/photos/fiskfisk/
433629365/

• Sport bike pic http://flickr.com/photos/
markhodgins/2447051098

• Yehudas RailsConf’08 slides for router code

• http://www.wikivs.com/wiki/
Merb_vs_Ruby_on_Rails for folder comparison

• Ezra and Yehuda for being the driving forces behind
the awesomeness that is Merb + Datamapper


Merb The Super Bike Of Frameworks

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