case-when のようなものを作ってみた

match.rb

# -*- coding: utf-8 -*-
module Kernel

  def match(obj, &blk)
    b = binding
    def b.if_that_is *something, &doing
      unless @matchers
        @matchers = {}
        @matchers.default = proc { nil }
      end
      something.each { |e|
        @matchers[e] = doing
      }
    end
    def b.or_else &doing
      @matchers ||= {}
      @matchers.default = doing
    end
    def b.method_missing funcname, *args
      $temporary_args = args
      if $temporary_args.empty?
        ret = eval "#{funcname}"
      else
        ret = eval "#{funcname}(*$temporary_args)"
      end
      $temporary_args = nil
      ret
    end
    b.instance_eval(&blk)
    b.send(:instance_variable_get, :@matchers)[obj].call
  end

end

if __FILE__ == $PROGRAM_NAME

  require "test/unit"
  class TestMatch < Test::Unit::TestCase

    def setup
    end

    def test_numbers
      res = nil
      match(5) {
        if_that_is(1, 2, 3) {
          res = false
        }
        if_that_is(4, 5) {
          res = true
        }
      }
      assert res
    end

    def test_strings
      res = nil
      match("Medli") {
        if_that_is("Medli") {
          res = true
        }
        if_that_is("Komali") {
          res = false
        }
      }
      assert res
    end

    def test_regexp
      res = nil
      match("Medli") {
        if_that_is(/^Me.li$/) {
          res = true
        }
        or_else {
          res = false
        }
      }
      assert res
    end

    def test_or_else
      res = nil
      match("Medli") {
        if_that_is("Komali") {
          res = false
        }
        or_else {
          res = true
        }
      }
      assert true
    end

  end

end