let.rb

require 'ostruct'

# Make little bundles of variables using Let {}
#
# example:
#   things = Let {
#     self.posts = Post.all
#     self.comments = Comment.where(post: posts)
#   }
#
#   puts things.posts
module Let
  class Object
    def initialize(&block)
      obj = OpenStruct.new
      obj.instance_eval(&block)

      @to_h = obj.to_h
    end

    attr_reader :to_h

    def method_missing(method, *args, &block)
      to_h[method] || super
    end
  end
end

def Let(&block)
  Let::Object.new(&block)
end

if __FILE__ == $0
  require 'test/unit'

  class LetTest < Test::Unit::TestCase
    def test_values
      obj = Let {
        self.a = 1
        self.b = a + 1
      }

      assert_equal 1, obj.a
      assert_equal 2, obj.b
    end

    def test_raises_when_missing
      assert_raise { Let {}.c }
    end

    def test_class_name
      assert_equal "Let::Object", Let{}.class.to_s
    end
  end
end