Class: Class

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

Instance Method Summary collapse

Instance Method Details

#class_attr_accessor(*names) ⇒ Object

Executes #class_attr_reader and #class_attr_writer.

Examples:


class Polygon
  class_attr_accessor :sides
end

Polygon.sides #=> nil
Polygon.sides = 5
Polygon.sides #=> 5
pentagon = Polygon.new
pentagon.sides #=> 5

See Also:



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# File 'lib/class_attr.rb', line 93

def class_attr_accessor(*names)
  class_attr_reader(*names)
  class_attr_writer(*names)
end

#class_attr_reader(*args) ⇒ Object

Defines a method that allows you to read an instance variable set at the class level. Also defines an instance method that reads the same thing. Comparable to #attr_reader for the class level.

So in summary defines: .var (which gets @var) and

#var (which gets self.class.var)

Examples:


class Polygon
  class_attr_reader :sides

  def self.is_a=(shape)
    case shape
      when 'triangle' then @sides = 3
      when 'square' then @sides = 4
    end
  end
end

Polygon.sides #=> nil
Polygon.is_a 'triangle'
Polygon.sides #=> 3
t = Polygon.new
t.sides #=> 3


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# File 'lib/class_attr.rb', line 29

def class_attr_reader(*args)
  names, default = separate_argument_list_and_default(args)
  names.each do |name|
    class_eval <<-EOS        
      def self.#{name}
        @#{name}
      end

      def #{name}
        self.class.send(:#{name})
      end
    EOS
    self.instance_variable_set("@#{name}", (default.dup rescue default))
  end
end

#class_attr_writer(*args) ⇒ Object

Defines a method for to write to an instance varaible set at the class level. Comparable to #attr_writer for the class level.

So in summary defines: .var= (which sets @var)

Examples:


class Polygon
  class_attr_writer :sides

  def self.rectangle?; @sides == 4; end
  def self.triangle?; @sides == 3; end
end

Polygon.rectangle? #=> false
Polygon.sides = 4
Polygon.rectangle? #=> true
Polygon.sides = 3
Polygon.triangle? #=> true


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# File 'lib/class_attr.rb', line 65

def class_attr_writer(*args)
  names, default = separate_argument_list_and_default(args)
  names.each do |name|
    class_eval <<-EOS        
      def self.#{name}=(obj)
        @#{name} = obj
      end
    EOS
  end
end

#inheritable_class_attr_accessor(*names) ⇒ Object

Executes #inheritable_class_attr_reader and #inheritable_class_attr_writer.

Examples:


class Polygon
  inheritable_class_attr_accessor :sides, :angles
  self.angles = [90]
end

class Triangle < Polygon
  self.sides = 3
  self.angles = [100, 35, 45]
end

class Rectangle < Polygon
  self.sides = 4
  self.angles << 60 << 100 << 110
end

class Square < Rectangle
  # should get 4 sides from rectange
  self.angles = [90] * 4
end

Polygon.sides    #=> nil
Triangle.sides   #=> 3
Rectangle.sides  #=> 4
Rectangle.angles #=> [90, 60, 100, 110]
Square.sides     #=> 4
Square.angles    #=> [90, 90, 90, 90]

See Also:



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# File 'lib/class_attr.rb', line 163

def inheritable_class_attr_accessor(*names)
  inheritable_class_attr_reader(*names)
  inheritable_class_attr_writer(*names)
end

#inheritable_class_attr_reader(*args) ⇒ Object

Creates a class and instance method to read the class level variable(s) with the name(s) provided. If no value has been set it attempts to use the value of the superclass.

See Also:



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# File 'lib/class_attr.rb', line 104

def inheritable_class_attr_reader(*args)
  names, default = separate_argument_list_and_default(args)
  names.each do |name|
    class_eval <<-EOS        
      def self.#{name}
        if @#{name}
          @#{name}
        elsif superclass.respond_to? :#{name}
          @#{name} ||= superclass.#{name}
        end
      end

      def #{name}
        self.class.send(:#{name})
      end
    EOS
    self.instance_variable_set("@#{name}", (default.dup rescue default))
  end
end

#inheritable_class_attr_writer(*args) ⇒ Object

The same as #class_attr_writer.



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# File 'lib/class_attr.rb', line 125

def inheritable_class_attr_writer(*args)
  class_attr_writer(*args)
end