1. Active Support
Core Extensions (3)
ROR lab. DD-1
- The 3rd round -
April 13, 2013
Hyoseong Choi

2. Ext. to Class
• class_attribute
active_support/core_ext/class/
attribute.rb
class A
class_attribute :x
end
class B < A; end
class C < B; end
A.x = :a
B.x # => :a
C.x # => :a
B.x = :b
A.x # => :a
C.x # => :b
C.x = :c
A.x # => :a
B.x # => :b
one or more inheritable class attributes that can be overridden at any level down the hierarchy

3. Ext. to Class
• class_inheritable_accessor, _reader, _writer
active_support/core_ext/class/
inheritable_attributes.rb
module ActionController
class Base
# FIXME: REVISE/SIMPLIFY THIS COMMENT.
# The value of allow_forgery_protection is inherited,
# but its value in a particular class does not affect
# the value in the rest of the controllers hierarchy.
class_inheritable_accessor :allow_forgery_protection
end
end
: deprecated ➜ class_attribute instead
accessors for class-level data which is inherited but not shared with children

4. class C; end
C.subclasses # => []
class B < C; end
C.subclasses # => [B]
class A < B; end
C.subclasses # => [B]
class D < C; end
C.subclasses # => [B, D]
Ext. to Class
• subclasses
active_support/core_ext/class/
subclasses.rb
C
B
A
D

5. Ext. to Class
• descendants
active_support/core_ext/class/
subclasses.rb
class C; end
C.descendants # => []
class B < C; end
C.descendants # => [B]
class A < B; end
C.descendants # => [B, A]
class D < C; end
C.descendants # => [B, A, D]
C
B
A
D

6. Ext. to String
• Strings “(html) unsafe” by default since Rails3
"".html_safe? # => false
s = "".html_safe
s.html_safe? # => true
• html_safe no escaping
s = "<script>...</script>".html_safe
s.html_safe? # => true
s # => "<script>...</script>"
active_support/core_ext/string/
output_safety.rb

7. Ext. to String
• html_safe
active_support/core_ext/string/
output_safety.rb
<%= raw @cms.current_template %>
<%== @cms.current_template %>
def raw(stringish)
stringish.to_s.html_safe
end

8. Ext. to String
• squish, squish!
active_support/core_ext/string/
filters.rb
" n foonr t bar n".squish # => "foo bar"

9. Ext. to String
• truncate
active_support/core_ext/string/
filters.rb
"Oh dear! Oh dear! I shall be late!".truncate(20)
# => "Oh dear! Oh dear!..."
"Oh dear! Oh dear! I shall be
late!".truncate(20, :omission => '&hellip;')
# => "Oh dear! Oh &hellip;" …
"Oh dear! Oh dear! I shall be late!".truncate(18)
# => "Oh dear! Oh dea..."
"Oh dear! Oh dear! I shall be
late!".truncate(18, :separator => ' ')
# => "Oh dear! Oh..."

10. Ext. to String
• Output safety - inquiry
active_support/core_ext/string/
inquiry.rb
"production".inquiry.production? # => true
"active".inquiry.inactive? # => false
a StringInquirer
object

11. Ext. to String
• Output safety - Key-based interpolation
active_support/core_ext/string/
interpolation.rb
"Total is %<total>.02f" % {:total => 43.1}
# => Total is 43.10
"I say %{foo}" % {:foo => "wadus"}
# => "I say wadus"
"I say %{woo}" % {:foo => "wadus"}
# => KeyError

12. Ext. to String
• Output safety - start_with? / ends_with?
active_support/core_ext/string/
starts_ends_with.rb
"foo".starts_with?("f") # => true
"foo".ends_with?("o") # => true

13. Ext. to String
• Output safety - strip_heredoc
active_support/core_ext/string/
strip.rb
if options[:usage]
puts <<-USAGE.strip_heredoc
This command does such and such.
Supported options are:
-h This message
...
USAGE
end

14. Ext. to String
• Access - at(position)
active_support/core_ext/string/
access.rb
"hello".at(0) # => "h"
"hello".at(4) # => "o"
"hello".at(-1) # => "o"
"hello".at(10) # => ERROR if < 1.9, nil in 1.9

15. Ext. to String
• Access - from(position)
active_support/core_ext/string/
access.rb
"hello".from(0) # => "hello"
"hello".from(2) # => "llo"
"hello".from(-2) # => "lo"
"hello".from(10) # => "" if < 1.9, nil in 1.9

16. Ext. to String
• Access - to(position)
active_support/core_ext/string/
access.rb
"hello".to(0) # => "h"
"hello".to(2) # => "hel"
"hello".to(-2) # => "hell"
"hello".to(10) # => "hello"

17. Ext. to String
• Access - first/last
active_support/core_ext/string/
access.rb
str.first(n) or str.to(n-1)
str.last(n) or str.from(-n)

18. Ext. to String
• Inflections
active_support/core_ext/string/
inflections.rb
• pluralize
• singularize
• camerlize
• underscore
• titleize
• dasherize
• demodulize
• deconstantize
• parameterize
• tableize
• classify
• constantize
• humanize
• foreign_key

19. ROR Lab.
감사합니다.