Active Support Core Extension (3)

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

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

Ext. to Class
• class_inheritable_accessor, _reader, _writer
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

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
subclasses.rb
C
B
A
D

Ext. to Class
• descendants
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

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

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

Ext. to String
• squish, squish!
filters.rb
" n foonr t bar n".squish # => "foo bar"

Ext. to String
• truncate
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 => '…')
# => "Oh dear! Oh …" …
"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..."

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

Ext. to String
• Output safety - Key-based interpolation
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

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

Ext. to String
• Output safety - strip_heredoc
strip.rb
if options[:usage]
  puts <<-USAGE.strip_heredoc
    This command does such and such.

    Supported options are:
      -h         This message
      ...
  USAGE
end

Ext. to String
• Access - at(position)
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

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

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

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

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

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