Module: ModelX::Percentage::ClassMethods

Defined in:
lib/model_x/percentage.rb

Instance Method Summary collapse

Instance Method Details

#percentage(*attributes) ⇒ Object

Adds percentage attributes for the given attribute. Per specified attribute, the following are added:

:<attribute>_percentage

Retrieves or accepts the value of the original times 100.

Usage

class MyObject
  include ModelX::Percentage

  attr_accessor :my_attribute
  percentage :my_attribute
end

Now, the following holds true:

object = MyObject.new

object.my_attribute = 0.5
object.my_attribute_percentage # => 50

object.my_attribute_percentage = 10
object.my_attribute # => 0.1

Note that an existing attribute reader must exist. For the writer to be defined, an existing attribute writer must exist.



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# File 'lib/model_x/percentage.rb', line 36

def percentage(*attributes)
  attributes.each do |attribute|

    # An attribute must already exist.
    unless instance_methods.include?(:"#{attribute}") || instance_methods.include?(:read_attribute)
      raise ArgumentError, "cannot add percentage attribute #{attribute} - no existing attribute exists"
    end

    define_writer = instance_methods.include?(:"#{attribute}=") || private_instance_methods.include?(:write_attribute)

    # Create a *_percentage reader and writer.
    class_eval "\n      def \#{attribute}_multiplier\n        1 - (\#{attribute}.to_f || 0)\n      end\n\n      def \#{attribute}_increase_multiplier\n        1 + (\#{attribute}.to_f || 0)\n      end\n\n      alias_method  :\#{attribute}_decrease_multiplier, :\#{attribute}_multiplier\n\n      def \#{attribute}_percentage\n        @\#{attribute}_percentage ||= if \#{attribute}.present?\n          \#{attribute}.to_f * 100\n        else\n          nil\n        end\n      end\n\n      def self.human_attribute_name(attribute, options = {})\n        if attribute =~ /_percentage$/\n          super $`, options\n        else\n          super\n        end\n      end\n\n    RUBY\n\n    if define_writer\n      validates_numericality_of :\"\#{attribute}_percentage\", :allow_blank => true\n\n      class_eval <<-RUBY, __FILE__, __LINE__+1\n\n        def \#{attribute}_percentage=(value)\n          if value.present?\n            @\#{attribute}_percentage = value\n            self.\#{attribute} = value.to_f / 100\n          else\n            @\#{attribute}_percentage = nil\n            self.\#{attribute} = nil\n          end\n        end\n\n      RUBY\n    end\n\n  end\nend\n", __FILE__, __LINE__+1