button_to_form

Motivation

The button_to provided by rails doesn't work when used inside of a <form> tag, because it adds a new <form> (at your current nesting level) and HTML doesn't allow a form to be nested within another form.

How does it work?

The HTML spec does, however, allow a button/input/etc. to be associated with a different form than the one it is nested within.

The HTML spec says:

A form-associated element is, by default, associated with its nearest ancestor form element (as described below), but, if it is listed, may have a form attribute specified to override this.

This helper takes advantage of that, rendering a separate, empty <form> in the footer, and then associating this button with it, so that it submits to that form's action rather than to the action of the form it is a descendant of.

So — assuming you have added <%= content_for(:footer) %> somewhere in your layout — this source:

= form_tag '/main_form' do
  = hidden_field_tag :main_form_param_1, 'main_form'
  = text_field_tag   :main_form_param_2, ''

  = button_to_form 'Make happy', '/make_happy' do
    = hidden_field_tag :how_happy, 'ecstatic!'

will get rendered to HTML that looks something like this:

  <form action="/main_form" accept-charset="UTF-8" method="post">
    <input type="hidden" name="main_form_param_1" id="main_form_param_1" value="main_form">
    <input type="text" name="main_form_param_2" id="main_form_param_2" value="">
    <button name="button" type="submit" form="form-1e7dc01b-46d0-4a44-908e-77fbe2a7ec98">Make happy</button>
  </form>
  …
  <div id="footer">
    <form id="form-1e7dc01b-46d0-4a44-908e-77fbe2a7ec98" action="/make_happy" accept-charset="UTF-8" method="post">
      <input type="hidden" name="how_happy" id="how_happy" value="ecstatic!">
    </form>
  </div>

As you can see, there are 2 <form> tags that get rendered, but neither of them is nested within the other, so it is allowed — and works well! Now you can include button_to calls inside of other forms as much as your heart desires.

Installation

Add this line to your application's Gemfile:

gem 'button_to_form'

For this helper to work, you must also include this somewhere in your layout:

  <%= content_for(:footer) %>

If you want these forms to be added to a different content_for key, say :forms, you can configure it like so:

ButtonToFormHelper.content_for_name = :forms

Usage

By default, it will generate a unique id for the form. In its simplest form, it can be used as a drop-in replacement for Rails's button_to. Example:

  = button_to_form 'Make happy', [:make_happy, user]

(These examples use HAML, but you could just as easily use ERB.)

Unless you have a use case where the default generated id doesn't work, it is recommended to use that approach, as it ensures that each button_to_form call has its own corresponding unique <form>.

If, however, you need to reference this form in other places, you can specify a well-known id as the form's id. You can also pass other form_options, such as method.

  = button_to_form 'Delete', thing,
    {data: {confirm: 'Are you sure?'}},
    {method: 'delete', id: 'delete_thing_form'}
  = hidden_field_tag :some_id, some_id, {form: 'delete_thing_form'}

You may pass along additional data to the endpoint via hidden_field_tags by passing them inside a block. You don't need to specify the form in this case because, as descendants, they are already associated with this new form.

  = button_to_form 'Delete', thing,
    {data: {confirm: 'Are you sure?'}},
    {method: 'delete'} do
    = hidden_field_tag :some_id, some_id

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To start up a development web server with the same internal Rails app that is used for tests, run rackup.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/TylerRick/button_to_form.