Reform with Rails

Last updated 07 May 2017 reform-rails v0.0

Reform works with any framework, but comes with additional Rails glue code.

Reform-Rails

The reform gem itself doesn’t contain any Rails-specific code but will still work, e.g. for JSON APIs. For extensive Rails support, add the reform-rails gem.

gem "reform", ">= 2.2.0"
gem "reform-rails"

Per default, reform-rails will assume you want ActiveModel::Validations as the validation engine. This will include the following into Reform::Form.

Form::ActiveModel for form builder compliance so your form works with form_for and friends.
Reform::Form::ActiveModel::FormBuilderMethods to make Reform consume Rails form builder’s weird parameters, e.g. {song_attributes: { number: 1 }}.
Uniqueness validation for ActiveRecord.

However, you can also use the new, recommended dry-validation backend, and you should check that out!

To do so, add the gem to your Gemfile.

gem "reform", ">= 2.2.0"
gem "reform-rails"
gem "dry-validation"

And configure Reform in an initializer, e.g. config/initializer/reform.rb to load the new validation backend.

 Rails.application.config.reform.validations = :dry

Make sure you use the API when writing dry validations.

Uniqueness Validation

Both ActiveRecord and Mongoid modules will support “native” uniqueness support from the model class when you use validates_uniqueness_of. They will provide options like :scope, etc.

You’re encouraged to use Reform’s non-writing unique: true validation, though. Learn more

ActiveModel Compliance

Forms in Reform can easily be made ActiveModel-compliant.

Note that this step is not necessary in a Rails environment.

class SongForm < Reform::Form
  include Reform::Form::ActiveModel
end

If you’re not happy with the model_name result, configure it manually via ::model.

class CoverSongForm < Reform::Form
  include Reform::Form::ActiveModel

  model :song
end

::model will configure ActiveModel’s naming logic. With Composition, this configures the main model of the form and should be called once.

This is especially helpful when your framework tries to render cover_song_path although you want to go with song_path.

FormBuilder Support

To make your forms work with all the form gems like simple_form or Rails form_for you need to include another module.

Again, this step is implicit in Rails and you don’t need to do it manually. If you’ve configured dry-validation as your validation framework the inclusion will not happen. You have to include at least the FormBuilderMethods module. This is needed to translate Rails’ suboptimal songs_attributes weirdness back to normal songs: naming in +#valiate+. This can be controlled via config.reform.enable_active_model_builder_methods = true.

class SongForm < Reform::Form
  include Reform::Form::ActiveModel
  include Reform::Form::ActiveModel::FormBuilderMethods
end

Simple Form

If you want full support for simple_form do as follows.

class SongForm < Reform::Form
  include Reform::Form::ActiveModel::ModelReflections

Including this module will add #column_for_attribute and other methods need by form builders to automatically guess the type of a property.

Validation Shortform

Luckily, this can be shortened as follows.

class SongForm < Reform::Form
  property :title, validates: {presence: true}
  property :length, validates: {numericality: true}
end

Use properties to bulk-specify fields.

class SongForm < Reform::Form
  properties :title, :length, validates: {presence: true} # both required!
  validates :length, numericality: true
end

Validations From Models

Sometimes when you still keep validations in your models (which you shouldn’t) copying them to a form might not feel right. In that case, you can let Reform automatically copy them.

class SongForm < Reform::Form
  property :title

  extend ActiveModel::ModelValidations
  copy_validations_from Song
end

Note how copy_validations_from copies over the validations allowing you to stay DRY.

This also works with Composition.

class SongForm < Reform::Form
  include Composition
  # ...

  extend ActiveModel::ModelValidations
  copy_validations_from song: Song, band: Band
end

ActiveRecord Compatibility

Reform provides the following ActiveRecord specific features. They’re mixed in automatically in a Rails/AR setup.

Uniqueness validations. Use validates_uniqueness_of in your form.

As mentioned in the Rails Integration section some Rails 4 setups do not properly load.

You may want to include the module manually then.

class SongForm < Reform::Form
  include Reform::Form::ActiveRecord

Mongoid Compatibility

Reform provides the following Mongoid specific features. They’re mixed in automatically in a Rails/Mongoid setup.

Uniqueness validations. Use validates_uniqueness_of in your form.