module ComparableByAttr

Allow simple definitions for object comparisons

Public Class Methods

attr_compare(*prec) click to toggle source

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)
# File lib/comparable_by_attr.rb, line 27
def self.attr_compare(*prec)
  attr_prec = prec.map do |attr|
    "@#{attr}".to_sym
  end
  @__attr_precedence = attr_prec
end
included(klass) click to toggle source

rubocop:disable Metrics/MethodLength class_eval wrapper

# 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

Public Instance Methods

<=>(other) click to toggle source
# File lib/comparable_by_attr.rb, line 34
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