RealForm

edit.html.erb

<% @my_form.render do |f| # custom form %>
  <div class="firstname"><%= f.firstname # maybe options are possible here %></div>
  <div class="text"><%= f.text %></div>
<% end %>



<%= @my_form.render # no customization %>

my_form.rb

Class MyForm < RealForm
  text_area :text, size: 100, label: "Some text", class: "funky class", validate: is_blah_blah
  
  input :firstname

  password :password, id: "the password"

  def is_blah_blah
    ...
  end
end

thing_controller.rb

def edit
  @my_form = MyForm.new()
end

def update
  @my_form = MyForm.new(params)

  if @my_form.valid?
    @mc_guffin.update_parameters(@my_form.to_hash)
  else
    flash.now @my_form.errors
  end
end