---
title: "Rails 6.1 raises an error for impossible camelcase inflections"
description:
  "Rails 6.1 raises an error if camelcase inflection is not possible with Rails
  generator"
canonical_url: "https://www.bigbinary.com/blog/rails-6-1-raises-error-for-impossible-camelcase-inflections"
markdown_url: "https://www.bigbinary.com/blog/rails-6-1-raises-error-for-impossible-camelcase-inflections.md"
---

# Rails 6.1 raises an error for impossible camelcase inflections

Rails 6.1 raises an error if camelcase inflection is not possible with Rails
generator

- Author: Yedhin Kizhakkethara
- Published: December 15, 2020
- Categories: Rails, Rails 6.1

From Rails 6.1 onwards, the default behavior of the Rails generator when
encountering an impossible "camelCase" inflection would be to raise an error,
rather than generating  a name that will cause problems.

### What are impossible "camelCase" inflections?

The
[Rails Inflector](https://api.rubyonrails.org/classes/ActiveSupport/Inflector/Inflections.html)
is part of the `ActiveSupport` module, and it comes shipped with patterns to
transform Ruby strings. This library is responsible for pluralization and/or
singularization of strings.

The Inflector tries its best to provide the desired result given a string. But
sometimes, with certain words, it can't provide say the pluralized version out
of the box.

Let's say for example the string is `DSL`. The desired plural form is `DSLs`.
But the Inflector gets confused on what exactly is the desired plural form or
more accurately what exactly is the underscore resource name and it used to
generate inconsistent class names.

### Before Rails 6.1

Let's try out the following example.

```bash
bundle exec rails g scaffold DSL field
```

In the output we can see that the controller filename is `ds_ls_controller.rb`
and the controller class name is:

```ruby
class DsLsController < ApplicationController
```

And the routes file is populated with:

```ruby
resources :dsls
```

You see the problem right?

The generated route `:dsls` expects a `DslsController` controller but the
controller generated is `DsLsController`. This will lead to a routing error.

### How Rails 6.1 solves this problem?

The Rails team decided that it would be better to terminate the generation
process with an error rather than generating classes that are internally
inconsistent.

Thus Rails now raises an error in the following two scenarios where the casing
is impossible to be inflected:

The first case is when "camelCased" model name is passed to a generator. The
second case is when the full round trip from pluralize to singularize does not
match with the original singular value. Rails checks for the following
condition.

```ruby
name.pluralize.underscore.singularize != name.underscore.singularize
```

We can try out the same example that we did in the previous section and it will
provide the following output:

```text
Rails cannot recover the underscored form from its camelcase form 'DSL'.
Please use an underscored name instead, either 'dsl' or 'ds_l'.
Or set up custom inflection rules for this noun before running the generator in config/initializers/inflections.rb.
```

This allows the developers to either rephrase the resource name with an
underscored name from the very beginning itself or follow the suggestion, that
is to create a custom inflection.

### Creating a custom inflection

`ActiveSupport::Inflector` provides us with the `inflections` method in order to
create our own custom inflections. This method can even accept an optional
locale, which comes in handy when we are writing inflection rules for languages
other than `:en`, which is the default locale.

You can have a detailed look into the inflection methods over
[here](https://api.rubyonrails.org/classes/ActiveSupport/Inflector/Inflections.html).

Let's try to make the above example work and get the desired underscore name for
the string `DSL`. We’re dealing with an irregular inflection. Thus we can make
use of the `irregular` method, which takes two arguments: the singular and the
plural form of the word as strings.

Let's just add the custom inflection into `config/initializers/inflections.rb`:

```ruby
# We provide the string in lowercase format
ActiveSupport::Inflector.inflections(:en) do |inflect|
  inflect.irregular 'dsl', 'dsls'
end
```

Voila! That's it.

Now if we run `rails g scaffold DSL`, we will be able to get the correct file
and class names.

Check out the [pull request](https://github.com/rails/rails/pull/39832) and
[the issue](https://github.com/rails/rails/issues/39117) for more details.

## Links

- [Human page](https://www.bigbinary.com/blog/rails-6-1-raises-error-for-impossible-camelcase-inflections)