couchrest_model/lib/couchrest/support/class.rb

# Copyright (c) 2006-2009 David Heinemeier Hansson
#  
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#  
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#  
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# Extracted From
# http://github.com/rails/rails/commit/971e2438d98326c994ec6d3ef8e37b7e868ed6e2

# Extends the class object with class and instance accessors for class attributes,
# just like the native attr* accessors for instance attributes.
#
#  class Person
#    cattr_accessor :hair_colors
#  end
#
#  Person.hair_colors = [:brown, :black, :blonde, :red]
class Class
  def cattr_reader(*syms)
    syms.flatten.each do |sym|
      next if sym.is_a?(Hash)
      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        unless defined? @@#{sym}  # unless defined? @@hair_colors
          @@#{sym} = nil          #   @@hair_colors = nil
        end                       # end
                                  #
        def self.#{sym}           # def self.hair_colors
          @@#{sym}                #   @@hair_colors
        end                       # end
                                  #
        def #{sym}                # def hair_colors
          @@#{sym}                #   @@hair_colors
        end                       # end
      EOS
    end
  end unless Class.respond_to?(:cattr_reader)

  def cattr_writer(*syms)
    options = syms.extract_options!
    syms.flatten.each do |sym|
      class_eval(<<-EOS, __FILE__, __LINE__ + 1)
        unless defined? @@#{sym}                       # unless defined? @@hair_colors
          @@#{sym} = nil                               #   @@hair_colors = nil
        end                                            # end
                                                       #
        def self.#{sym}=(obj)                          # def self.hair_colors=(obj)
          @@#{sym} = obj                               #   @@hair_colors = obj
        end                                            # end
                                                       #
        #{"                                            #
        def #{sym}=(obj)                               # def hair_colors=(obj)
          @@#{sym} = obj                               #   @@hair_colors = obj
        end                                            # end
        " unless options[:instance_writer] == false }  # # instance writer above is generated unless options[:instance_writer] == false
      EOS
    end
  end unless Class.respond_to?(:cattr_writer)

  def cattr_accessor(*syms)
    cattr_reader(*syms)
    cattr_writer(*syms)
  end unless Class.respond_to?(:cattr_accessor)
  
  # Defines class-level inheritable attribute reader. Attributes are available to subclasses,
  # each subclass has a copy of parent's attribute.
  #
  # @param *syms<Array[#to_s]> Array of attributes to define inheritable reader for.
  # @return <Array[#to_s]> Array of attributes converted into inheritable_readers.
  #
  # @api public
  #
  # @todo Do we want to block instance_reader via :instance_reader => false
  # @todo It would be preferable that we do something with a Hash passed in
  #   (error out or do the same as other methods above) instead of silently
  #   moving on). In particular, this makes the return value of this function
  #   less useful.
  def extlib_inheritable_reader(*ivars)
    instance_reader = ivars.pop[:reader] if ivars.last.is_a?(Hash)

    ivars.each do |ivar|
      self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
        def self.#{ivar}
          return @#{ivar} if self.object_id == #{self.object_id} || defined?(@#{ivar})
          ivar = superclass.#{ivar}
          return nil if ivar.nil? && !#{self}.instance_variable_defined?("@#{ivar}")
          @#{ivar} = ivar && !ivar.is_a?(Module) && !ivar.is_a?(Numeric) && !ivar.is_a?(TrueClass) && !ivar.is_a?(FalseClass) ? ivar.dup : ivar
        end
      RUBY
      unless instance_reader == false
        self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
          def #{ivar}
            self.class.#{ivar}
          end
        RUBY
      end
    end
  end unless Class.respond_to?(:extlib_inheritable_reader)

  # Defines class-level inheritable attribute writer. Attributes are available to subclasses,
  # each subclass has a copy of parent's attribute.
  #
  # @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to
  #   define inheritable writer for.
  # @option syms :instance_writer<Boolean> if true, instance-level inheritable attribute writer is defined.
  # @return <Array[#to_s]> An Array of the attributes that were made into inheritable writers.
  #
  # @api public
  #
  # @todo We need a style for class_eval <<-HEREDOC. I'd like to make it
  #   class_eval(<<-RUBY, __FILE__, __LINE__), but we should codify it somewhere.
  def extlib_inheritable_writer(*ivars)
    instance_writer = ivars.pop[:writer] if ivars.last.is_a?(Hash)
    ivars.each do |ivar|
      self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
        def self.#{ivar}=(obj)
          @#{ivar} = obj
        end
      RUBY
      unless instance_writer == false
        self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
          def #{ivar}=(obj) self.class.#{ivar} = obj end
        RUBY
      end

      self.send("#{ivar}=", yield) if block_given?
    end
  end unless Class.respond_to?(:extlib_inheritable_writer)

  # Defines class-level inheritable attribute accessor. Attributes are available to subclasses,
  # each subclass has a copy of parent's attribute.
  #
  # @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to
  #   define inheritable accessor for.
  # @option syms :instance_writer<Boolean> if true, instance-level inheritable attribute writer is defined.
  # @return <Array[#to_s]> An Array of attributes turned into inheritable accessors.
  #
  # @api public
  def extlib_inheritable_accessor(*syms, &block)
    extlib_inheritable_reader(*syms)
    extlib_inheritable_writer(*syms, &block)
  end unless Class.respond_to?(:extlib_inheritable_accessor)
end

class Array
  # Extracts options from a set of arguments. Removes and returns the last
  # element in the array if it's a hash, otherwise returns a blank hash.
  #
  #   def options(*args)
  #     args.extract_options!
  #   end
  #
  #   options(1, 2)           # => {}
  #   options(1, 2, :a => :b) # => {:a=>:b}
  def extract_options!
    last.is_a?(::Hash) ? pop : {}
  end unless Array.respond_to?(:extract_options!)
end