‘Iacta alea est’

Basic Form: Formtastic

If we turn our attention to Formtastic then we can create a form using our model object from default Rails.

Formtastic is a layer of syntactic sugar upon Rails default form builder.

<%= semantic_form_for @form,
    as: :subscription,
    url: email_subscriptions_path do |f| %>
  <%= f.input :email, 
      label: "Email address",
      hint: "We'll never share your email with anyone else." %>
  <%= f.action :submit, 
      as: :button,
      label: "Submit" %>
<% end %>

I think this is enough to get us what we want. There is one distinction worth noting: Formtastic defaults to an li as a wrapper for the form-control. That’s not such a big deal, and more semantically correct if we’re being pedantic.

I think there are a few things that are interesting here. Given our categories and the hierarchy then Formtastic really does seem to capture the definition of a field at the right level.

The attribute, label and hint are all specified at the top level, being the key concerns in the template. Formtastic automatically chooses input[type=email] based on the attribute name containing the string "email", so the mapping is implicit.

The errors are invisible being an internal concern. The input is the central element that is then wrapped by the hint/help text and, optionally, the error message.

Here we see that explicitly in the code:

# Formtastic::Inputs::Base::Wrapping

def input_wrapping(&block)
    [template.capture(&block), error_html, hint_html].join("\n").html_safe,

Where the input is itself wrapping the original Rails method:

# Formtastic::Inputs::EmailInput

def to_html
  input_wrapping do
    label_html <<
    builder.email_field(method, input_html_options)

The label lives together with the field.

If we flatten that out then we see all four aspects:


I think I like this succinctness but part of me would prefer this mapping to live outside of the template itself.

Thursday 24th June 2021.