Suggestions for Rails Enums -- detailed writeup

I wrote up this detailed description of the issues I’m having with Rails Enums:

Enums and Queries in Rails 4.1, and Understanding Ruby

At the bottom of the article, I post my recommendation:

Recommendations to the Rails Core Team

In response to this issue, I submitted this github issue: Rails where query should see value is an enum and convert a string #17226

  1. @Bounga and @rafaelfranca on Github suggest that we can’t automatically convert enum string values in queries. I think that is true for converting cases of a ? or a named param, but I suspect that a quick map lookup to see that the attribute is an enum, and a string is passed, and then converting the string value to an integer is the right thing to do for 2 reasons:

  2. This is the sort of “magic” that I expect from Rails.

  3. Existing methods find_or_initialize_by and find_or_create_by will result in obscure bugs when string params are passed for enums.
    However, it’s worth considering if all default accessor methods (setters) should be consistently be called for purposes of passing values in a map to such methods. I would venture that Rails enums are some Rails provided magic, and thus they should have a special case. If this shouldn’t go into Rails, then possibly a gem extension could provide a method like Model.where_with_enum which would convert a String into the proper numerical value for the enum. I’m not a huge fan of the generated Model scopes for enums, as I like to see what database field is being queried against.

1

assert_equal 0, type.type_cast_from_user(‘bad’)


Aside from putting automatic conversion of the enum hash attributes, I recommend we change the automatic conversion of Strings to integers to use the stricter `Integer(some_string)` rather than `some_string.to_i`. The difference is considerable, `String#to_i` is extremely permissive. Try it in a console. With the `to_i` method, any number characters at the beginning of the String are converted to an Integer. If the first character is not a number, **0 is returned**, which is almost certainly a default enum value. Thus, this simple change would make it **extremely** clear when an enum string is improperly used. I would guess that this would make some existing code crash, but in all circumstances for a valid reason. As to whether this change should be done for all integer attributes is a different discussion, as that could have backwards compatibility ramifications. This change would require changing the tests in [ActiveRecord::ConnectionAdapters::TypesTest](https://github.com/rails/rails/blob/master/activerecord/test/cases/types_test.rb). For example, this test:
would change to throw an exception, unless the cases are restricted to using Integer.new() for enums. It is inconsistent that some type conversions throw exceptions, such as converting a symbol to an integer. Whether or not they should is much larger issue. In the case of enums, **I definitely believe that proper enum string value should not silently convert to zero every time.**

I definitely agree that there are some ‘gotchas’ here.

I can’t think of any disadvantages to switching to using Integer() instead of to_i - as you say, this would only raise an exception in instances where the user has a bug in their code, which is a good thing to discover. I don’t think we could change this elsewhere though.

I also think having a new scope for the enum generated such as Conversation.with_status(string_or_num_status) would be a nice helper in cases where you have a dynamic value as it lets you avoid the alternative Conversation.send(@some_conversation.status) or Conversation.where(status: Conversation.statuses(@some_conversation.status)).

Thank you both for this conversation.

I thought of bringing up in this thread a few points related to conversations such as: https://github.com/rails/rails/issues/13971

Is there any plan to make enum so that it can be used ‘to expose user-facing attributes’ ?
It would be really awesome to use this kind of optimizations not just for managing the internal states of the application.

Thank you for the awesome work
Stefano

Hi Stefano,

Thanks for your comments. I would have contributed a PR, but I didn’t get any suggestion from the core members that this would make sense. It seems like they are working on something for Rails 5.

Consider posting: http://forum.railsonmaui.com/t/enums-and-queries-in-rails-4-1-and-understanding-ruby/118/6

Aloha,

Justin

Hi Justin, thanks for the response, I did read your great article a few days ago, thank you :slight_smile:
I also noticed this conversation: So it seems there are already some improvements for rails 5 however it seems this is still considered an internal feature and not so much a user facing feature, is this still the case?Thanks for linking to the comments on your website I took a quick look at interesting indeed.Thanks again!Stefano

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