vendor/rails/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb

   1 # Retain for backward compatibility.  Methods are now included in Class.
   2 module ClassInheritableAttributes # :nodoc:
   3 end
   4
   5 # Allows attributes to be shared within an inheritance hierarchy, but where each descendant gets a copy of
   6 # their parents' attributes, instead of just a pointer to the same. This means that the child can add elements
   7 # to, for example, an array without those additions being shared with either their parent, siblings, or
   8 # children, which is unlike the regular class-level attributes that are shared across the entire hierarchy.
   9 class Class # :nodoc:
  10   def class_inheritable_reader(*syms)
  11     syms.each do |sym|
  12       next if sym.is_a?(Hash)
  13       class_eval <<-EOS
  14         def self.#{sym}
  15           read_inheritable_attribute(:#{sym})
  16         end
  17
  18         def #{sym}
  19           self.class.#{sym}
  20         end
  21       EOS
  22     end
  23   end
  24
  25   def class_inheritable_writer(*syms)
  26     options = syms.extract_options!
  27     syms.each do |sym|
  28       class_eval <<-EOS
  29         def self.#{sym}=(obj)
  30           write_inheritable_attribute(:#{sym}, obj)
  31         end
  32
  33         #{"
  34         def #{sym}=(obj)
  35           self.class.#{sym} = obj
  36         end
  37         " unless options[:instance_writer] == false }
  38       EOS
  39     end
  40   end
  41
  42   def class_inheritable_array_writer(*syms)
  43     options = syms.extract_options!
  44     syms.each do |sym|
  45       class_eval <<-EOS
  46         def self.#{sym}=(obj)
  47           write_inheritable_array(:#{sym}, obj)
  48         end
  49
  50         #{"
  51         def #{sym}=(obj)
  52           self.class.#{sym} = obj
  53         end
  54         " unless options[:instance_writer] == false }
  55       EOS
  56     end
  57   end
  58
  59   def class_inheritable_hash_writer(*syms)
  60     options = syms.extract_options!
  61     syms.each do |sym|
  62       class_eval <<-EOS
  63         def self.#{sym}=(obj)
  64           write_inheritable_hash(:#{sym}, obj)
  65         end
  66
  67         #{"
  68         def #{sym}=(obj)
  69           self.class.#{sym} = obj
  70         end
  71         " unless options[:instance_writer] == false }
  72       EOS
  73     end
  74   end
  75
  76   def class_inheritable_accessor(*syms)
  77     class_inheritable_reader(*syms)
  78     class_inheritable_writer(*syms)
  79   end
  80
  81   def class_inheritable_array(*syms)
  82     class_inheritable_reader(*syms)
  83     class_inheritable_array_writer(*syms)
  84   end
  85
  86   def class_inheritable_hash(*syms)
  87     class_inheritable_reader(*syms)
  88     class_inheritable_hash_writer(*syms)
  89   end
  90
  91   def inheritable_attributes
  92     @inheritable_attributes ||= EMPTY_INHERITABLE_ATTRIBUTES
  93   end
  94
  95   def write_inheritable_attribute(key, value)
  96     if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
  97       @inheritable_attributes = {}
  98     end
  99     inheritable_attributes[key] = value
 100   end
 101
 102   def write_inheritable_array(key, elements)
 103     write_inheritable_attribute(key, []) if read_inheritable_attribute(key).nil?
 104     write_inheritable_attribute(key, read_inheritable_attribute(key) + elements)
 105   end
 106
 107   def write_inheritable_hash(key, hash)
 108     write_inheritable_attribute(key, {}) if read_inheritable_attribute(key).nil?
 109     write_inheritable_attribute(key, read_inheritable_attribute(key).merge(hash))
 110   end
 111
 112   def read_inheritable_attribute(key)
 113     inheritable_attributes[key]
 114   end
 115
 116   def reset_inheritable_attributes
 117     @inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
 118   end
 119
 120   private
 121     # Prevent this constant from being created multiple times
 122     EMPTY_INHERITABLE_ATTRIBUTES = {}.freeze unless const_defined?(:EMPTY_INHERITABLE_ATTRIBUTES)
 123
 124     def inherited_with_inheritable_attributes(child)
 125       inherited_without_inheritable_attributes(child) if respond_to?(:inherited_without_inheritable_attributes)
 126
 127       if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
 128         new_inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
 129       else
 130         new_inheritable_attributes = inheritable_attributes.inject({}) do |memo, (key, value)|
 131           memo.update(key => (value.dup rescue value))
 132         end
 133       end
 134
 135       child.instance_variable_set('@inheritable_attributes', new_inheritable_attributes)
 136     end
 137
 138     alias inherited_without_inheritable_attributes inherited
 139     alias inherited inherited_with_inheritable_attributes
 140 end