evanphx (owner)

Revisions

gist: 193752 Download_button fork
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class Attributes
  def initialize(parent)
    @parent = parent
    @children = []
    @values = {}
    @origins = {}
 
    parent.add_child(self) if parent
  end
 
  def add_child(child)
    @children << child
  end
 
  def get(key)
    if @values.key?(key)
      return @values[key]
    end
 
    origin, value = @parent.find(key)
    if value
      @values[key] = value
      @origins[key] = origin
      return value
    end
 
    # not found in any parent
    return nil
  end
 
  def find(key)
    if @values.key?(key) and !@origins[key]
      return self, @values[key]
    end
 
    if @parent
      @parent.find(key)
    else
      nil
    end
  end
 
  def set(key, val)
    @values[key] = val
    @origins[key] = nil
 
    @children.each { |c| c.set_inherited(key, val, self) }
  end
 
  def set_inherited(key, val, who)
    # ignore requests to set values we set on ourselves
    return if @origins.key?(key) and !@origins[key]
 
    @values[key] = val
    @origins[key] = who
 
    @children.each { |c| c.set_inherited(key, val, who) }
  end
end
 
class Cave
  def self.inherited(obj)
    obj.setup_attributes(self)
  end
 
  def self.setup_attributes(parent)
    @attributes = Attributes.new(parent.attributes)
  end
 
  def self.attributes
    @attributes ||= Attributes.new(nil)
  end
 
  def self.kind
    attributes.get :kind
  end
 
  def self.set_kind(which)
    attributes.set :kind, which
  end
end
 
Cave.set_kind "beach side"
p Cave.kind # beach side
 
class Sub1 < Cave
end
 
# == parent push values to children that inherited values
 
p Sub1.kind # beach side
Cave.set_kind "mountain"
p Cave.kind # mountain
p Sub1.kind # mountain
 
 
# == child sets it's own value
 
Sub1.set_kind "underwater"
p Sub1.kind # underwater
 
# == parent sets don't flow into children with own values
 
Cave.set_kind "mountain top"
p Cave.kind # mountain top
p Sub1.kind # underwater
 
# == multiple depth children
 
class Sub2 < Cave
end
 
p Sub2.kind # mountain top
 
class Sub3 < Sub2
end
 
p Sub3.kind # mountain top
 
# == set on influences subclasses only
 
Sub2.set_kind "moon"
 
p Sub2.kind # moon
p Sub3.kind # moon
 
Cave.set_kind "desert"
 
p Sub2.kind # moon
p Sub3.kind # moon
 
Sub2.set_kind "martian"
 
p Sub3.kind # martian