a custom Rails *_for helper?

Question

I find myself using Rails' form_for in the show view to take advantage of translations and other methods on AR objects to create non-interactive forms to display the object. There's got to be a better way to do this though with a custom builder. Is there anything out there (gem or diy-tutorial-wise) for this kind of functionality? My search skills are poor for this one.

For example, it be great if I could write something like this:

<%= dl_for(@cog) do |dl| %>
  <%= dl.dt_dd(:name) %>
  <%= dl.dt_dd(:colors) { |colors| colors.to_sentence } %>
  <%= dl.dt_dd(:size, { class: @cog.size }) %>
<% end %>

And get:

<dl>
  <dt>My Name Translation</dt>
  <dd>Cog 1</dd>

  <dt>My Colors Translation</dt>
  <dd>Red, Green and Blue</dd>

  <dt class="Small">My Size Translation</dt>
  <dd class="Small">Small</dd>
</dl>

Answer 1

You can use a variation of the presenter pattern to create your own element builders:

class DefinitionListBuilder
  attr_reader :object
  # context is the view context that we can call the rails helper
  # method on
  def initialize(object, context, **options)
    @object = object
    @context = context
    @options = options
    @i18n_key = object.model_name.i18n_key
  end

  def h
    @context
  end

  def dl(&block)
    @context.content_tag :dl, @options do
      yield self
    end
  end

  def dt_dd(attribute, **options)
    h.capture do
      h.concat(h.content_tag :dt, translate_attribute(attribute), options)
      h.concat(h.content_tag :dd, object.send(attribute), options)
    end
  end

  private
  def translate_attribute(attribute)
    key = "activerecord.attributes.#{@i18n_key}.#{attribute}"
    h.t(key)
  end
end

This plain old ruby object is the equivalent to a FormBuilder. Which really just is a object that wraps a model instance and provides helpers scoped to that instance. You then create a helper which creates instances of the element builder:

module DefinitionListHelper
  def dl_for(record, **options, &block)
    builder = DefinitionListBuilder.new(record, self, options)
    builder.dl(&block)
  end
end

This is the equivalent to ActionView::Helpers::FormHelper which provides form_for.

For the sake of brevity this is simplified and #dd_dt does not take a block.

Example:

# config/locales/se.yml
se:
  activerecord:
    attributes:
      cog:
        name: 'Namn'
        size: 'Storlek'
        color: 'Färg'

<%= dl_for(Cog.new(name: 'Cogsworth', size: 'biggish', color: 'red')) do |builder| %>
  <%= builder.dt_dd :name %>
  <%= builder.dt_dd :size %>
  <%= builder.dt_dd :color %>
<% end %>

HTML output:

<dl>
  <dt>Namn</dt><dd>Cogsworth</dd>
  <dt>Storlek</dt><dd>biggish</dd>
  <dt>Färg</dt><dd>red</dd>
</dl>