http://www.linux-mag.com/cache/7478/1.html
http://www.linux-mag.com/cache/7484/1.html
http://www.linux-mag.com/cache/7489/1.html
http://www.linux-mag.com/id/7492/
Just some nice things in Rails 3.0 that might be useful in a hobo
context ;)
Anyone using Hobo with Rails 3.0 out there? How do they currently fit?
Validations
--------------
class Wheels < ActiveRecord::Validator
def validate
number_of_wheels = options[ :number_of_wheels ] || 4
if record.number_of_wheels != number_of_wheels
record.errors[ :number_of_wheels ] << "Your #{record.class}
won't run"
end
end
end
class Engine < ActiveRecord::Validator
def validate
# Valid?
end
end
class Weight < ActiveRecord::Validator
def validate
# Valid?
end
end
class Vehicle < ActiveRecord::Base
attr_accessor :number_of_wheels
end
class Car < Vehicle
validates_with Wheels, :number_of_wheels => 4
validates_with Engine, Weight
end
class Motorcycle < Vehicle
validates_with Wheels, :number_of_wheels => 2
end
..."validates_with encapsulates rules and makes those rules reusable
akin to any other class. I can imagine modules and gems full of
validator classes for email, telephone numbers, and common formats
that are best written once and shared among many applications.
Thankfully, I was able to reuse some code — Wheels — even in this
limited example."
State machine
-------------------
Several plugins provide state machines for Rails, but the feature is
so fundamental, the best features of available solutions were
integrated into the core to create ActiveRecord::StateMachine.
state_machine do
state :placed # In limbo
state :paid
...
event :advance_order do
transitions :to => :paid, :from => [ :placed ],
:on_transition => :pick_list
transitions :to => :assembled,:from => [ :paid ],
...
end
...
end
Hmm, I think there is some overlap with hobo here... but perhaps the
hobo solution is even more powerful and flexible?
---
Selection drop-downs
grouped_collection_select(:city, :country_id,
@continents, :countries,
:name, :id, :name)
… produces:
<select name="city[country_id]">
<optgroup label="Africa">
<option value="1">South Africa</option>
<option value="3">Somalia</option>
</optgroup>
<optgroup label="Europe">
<option value="7" selected="selected">Denmark</option>
<option value="2">Ireland</option>
</optgroup>
</select>
Try!!!
------
Student.find_by_name( 'joe' ).try( :homeroom ).try(: teacher )
Scopes
----------
class Student < ActiveRecord::Base
default_scope :order => 'last_name ASC'
named_scope :seniors, :conditions => { :year => 'senior' }
end
The default scope imposes a sort order on all results from
Student.find*(). The named scope invents the method Student.seniors()
to be the analog of Student.find(:all, :conditions => { :year =>
'senior' }. Ultimately, the combination of scopes produce a query such
as SELECT * FROM `students` WHERE `year`='senior' ORDER BY `last_name`
ASC for Student.seniors(). Again, which code would you prefer to write
and read?
You can now scope dynamically, too. This code…
Student.scoped_by_year( 'senior' ).find( :all )
… is the equivalent of the named scope
DRY RESTful controllers
---------------------------------
Edge Rails does away with all that cruft and reduces the same
controller method to this:
respond_to :html, :xml
def create
@student = Student.new(params[:student])
flash[:notice] = 'Student was successfully created.' if
@student.save
respond_with(@student)
end
respond_with() deduces what format is required and attempts to find a
view associated with the action and the format.
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