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Contents
#--
# NOTE Better as a parameterized mixin?
#++
class Module
# Automatically generate sorting defintions base on attribute fields.
#
# sort_on :a, :b
#
# _is equivalent to_
#
# def <=>(o)
# cmp = self.a <=> o.a; return cmp unless cmp == 0
# cmp = self.b <=> o.b; return cmp unless cmp == 0
# 0
# end
#
def sort_on(*fields)
code = %{def <=>(o)\n}
fields.each { |f|
code << %{cmp = ( @#{f} <=> o.instance_variable_get('@#{f}') );
return cmp unless cmp == 0\n}
}
code << %{0\nend; alias_method :cmp, :<=>;}
class_eval( code )
fields
end
# Should this be a standard alias?
alias_method :compare_on, :sort_on
# Deprecated usage
alias_method :sort_attributes, :sort_on
end
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TCModule < Test::Unit::TestCase
def test_sort_on
c = Class.new
c.class_eval {
def initialize(a,b)
@a=a; @b=b
end
sort_on :a,:b
}
a = [c.new(10,20),c.new(10,30)]
assert_equal( a, a.sort )
a = [c.new(10,30),c.new(10,20)]
assert_equal( a.reverse, a.sort )
a = [c.new(10,10),c.new(20,10)]
assert_equal( a, a.sort )
a = [c.new(20,10),c.new(10,10)]
assert_equal( a.reverse, a.sort )
a = [c.new(10,30),c.new(20,10)]
assert_equal( a, a.sort )
end
end
=end
Version data entries
26 entries across 26 versions & 1 rubygems