Class: Class

Inherits:
Object
  • Object
show all
Defined in:
lib/class_inheritable_attributes.rb

Overview

Allows attributes to be shared within an inheritance hierarchy. Each descendant gets a copy of their parents’ attributes, instead of just a pointer to the same. This means that the child can add elements to, for example, an array without those additions being shared with either their parent, siblings, or children. This is unlike the regular class-level attributes that are shared across the entire hierarchy.

The copies of inheritable parent attributes are added to subclasses when they are created, via the inherited hook.

class Person
  class_inheritable_accessor :hair_colors
end

Person.hair_colors = [:brown, :black, :blonde, :red]
Person.hair_colors     # => [:brown, :black, :blonde, :red]
Person.new.hair_colors # => [:brown, :black, :blonde, :red]

To opt out of the instance writer method, pass :instance_writer => false. To opt out of the instance reader method, pass :instance_reader => false.

class Person
  class_inheritable_accessor :hair_colors :instance_writer => false, :instance_reader => false
end

Person.new.hair_colors = [:brown]  # => NoMethodError
Person.new.hair_colors             # => NoMethodError

Instance Method Summary collapse

Instance Method Details

#class_inheritable_accessor(*syms) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 105

def class_inheritable_accessor(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_writer(*syms)
end

#class_inheritable_array(*syms) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 110

def class_inheritable_array(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_array_writer(*syms)
end

#class_inheritable_array_writer(*syms) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 71

def class_inheritable_array_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}=(obj)                          # def self.levels=(obj)
        write_inheritable_array(:#{sym}, obj)        #   write_inheritable_array(:levels, obj)
      end                                            # end
                                                     #
      #{"                                            #
      def #{sym}=(obj)                               # def levels=(obj)
        self.class.#{sym} = obj                      #   self.class.levels = obj
      end                                            # end
      " unless options[:instance_writer] == false }  # # the writer above is generated unless options[:instance_writer] == false
    EOS
  end
end

#class_inheritable_hash(*syms) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 115

def class_inheritable_hash(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_hash_writer(*syms)
end

#class_inheritable_hash_writer(*syms) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 88

def class_inheritable_hash_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}=(obj)                          # def self.nicknames=(obj)
        write_inheritable_hash(:#{sym}, obj)         #   write_inheritable_hash(:nicknames, obj)
      end                                            # end
                                                     #
      #{"                                            #
      def #{sym}=(obj)                               # def nicknames=(obj)
        self.class.#{sym} = obj                      #   self.class.nicknames = obj
      end                                            # end
      " unless options[:instance_writer] == false }  # # the writer above is generated unless options[:instance_writer] == false
    EOS
  end
end

#class_inheritable_reader(*syms) ⇒ Object

:nodoc:



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# File 'lib/class_inheritable_attributes.rb', line 36

def class_inheritable_reader(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    next if sym.is_a?(Hash)
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}                                # def self.after_add
        read_inheritable_attribute(:#{sym})          #   read_inheritable_attribute(:after_add)
      end                                            # end
                                                     #
      #{"                                            #
      def #{sym}                                     # def after_add
        self.class.#{sym}                            #   self.class.after_add
      end                                            # end
      " unless options[:instance_reader] == false }  # # the reader above is generated unless options[:instance_reader] == false
    EOS
  end
end

#class_inheritable_writer(*syms) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 54

def class_inheritable_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval(<<-EOS, __FILE__, __LINE__ + 1)
      def self.#{sym}=(obj)                          # def self.color=(obj)
        write_inheritable_attribute(:#{sym}, obj)    #   write_inheritable_attribute(:color, obj)
      end                                            # end
                                                     #
      #{"                                            #
      def #{sym}=(obj)                               # def color=(obj)
        self.class.#{sym} = obj                      #   self.class.color = obj
      end                                            # end
      " unless options[:instance_writer] == false }  # # the writer above is generated unless options[:instance_writer] == false
    EOS
  end
end

#inheritable_attributes ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 120

def inheritable_attributes
  @inheritable_attributes ||= EMPTY_INHERITABLE_ATTRIBUTES
end

#read_inheritable_attribute(key) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 141

def read_inheritable_attribute(key)
  inheritable_attributes[key]
end

#reset_inheritable_attributes ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 145

def reset_inheritable_attributes
  @inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
end

#write_inheritable_array(key, elements) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 131

def write_inheritable_array(key, elements)
  write_inheritable_attribute(key, []) if read_inheritable_attribute(key).nil?
  write_inheritable_attribute(key, read_inheritable_attribute(key) + elements)
end

#write_inheritable_attribute(key, value) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 124

def write_inheritable_attribute(key, value)
  if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
    @inheritable_attributes = {}
  end
  inheritable_attributes[key] = value
end

#write_inheritable_hash(key, hash) ⇒ Object 



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# File 'lib/class_inheritable_attributes.rb', line 136

def write_inheritable_hash(key, hash)
  write_inheritable_attribute(key, {}) if read_inheritable_attribute(key).nil?
  write_inheritable_attribute(key, read_inheritable_attribute(key).merge(hash))
end