Module: ComparableByAttr

Includes:
Comparable
Defined in:
lib/comparable_by_attr.rb

Overview

Allow simple definitions for object comparisons

Class Method Summary collapse

Class Method Details

.included(klass) ⇒ Object

rubocop:disable Metrics/MethodLength class_eval wrapper



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# File 'lib/comparable_by_attr.rb', line 6

def self.included(klass)
  klass.class_eval do
    @__attr_precedence = nil

    # attr_compare allows selection of specific instance variables and order
    # to use within the comparison of objects created off the class
    #
    # Example:
    #   class IgnoreC
    #     include ComparableByAttr
    #     attr_compare :a, :b
    #
    #     def initialize(a, b, c)
    #       @a = a
    #       @b = b
    #       @c = c
    #     end
    #   end
    #
    # Arguments:
    #   *prec = (Optional Precedence Map)
    def self.attr_compare(*prec)
      attr_prec = prec.map do |attr|
        "@#{attr}".to_sym
      end
      @__attr_precedence = attr_prec
    end

    def <=>(other)
      prec = self.class.instance_variable_get(:@__attr_precedence)
      comp_order = prec || instance_variables.sort
      this = comp_order.map { |field| instance_variable_get(field) }
      that = comp_order.map { |field| other.instance_variable_get(field) }
      this <=> that
    end
  end
end