Engineering Long-Lasting Software: An Agile Approach Using SaaS and Cloud Computing, Beta Edition by Patterson David & Fox Armando

Author:Patterson, David & Fox, Armando [Patterson, David]
Language: eng
Format: mobi, epub
ISBN: 9780984881208
Publisher: Strawberry Canyon LLC
Published: 2012-08-23T16:00:00+00:00

Both examples involve specifying constraints on entities or actions, and although there might be many places in an app where such constraints should be considered, the DRY philosophy urges us to centralize them in one place. Rails provides two analogous facilities for doing this: validations for models and filters for controllers.

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http://pastebin.com/2GtWshSb

1 class Movie < ActiveRecord::Base

2 RATINGS = %w[G PG PG-13 R NC-17] # %w[] shortcut for array of strings

3 validates :title, :presence => true

4 validates :release_date, :presence => true

5 validate :released_1930_or_later # uses custom validator below

6 validates :rating, :inclusion => {:in => RATINGS}, :unless => :grandfathered?

7 def released_1930_or_later

8 errors.add(:release_date, ’must be 1930 or later’) if

9 self.release_date < Date.parse(’1 Jan 1930’)

10 end

11 def grandfathered? ; self.release_date >= @@grandfathered_date ; end

12

13 end

14 # try in console:

15 m = Movie.new(:title => ’’, :rating => ’RG’, :release_date => ’1929-01-01’)

16 # force validation checks to be performed:

17 m.valid? # => false

18 m.errors[:title] # => ["can’t be blank"]

19 m.errors[:rating] # => ["is not included in the list"]

20 m.errors[:release_date] # => ["must be 1930 or later"]

21 m.errors.full_messages # => ["Title can’t be blank", "Rating is not included in the list", "Release date must be 1930 or later"]

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