This is going to be short because I’ve been crazy busy, but nothing really worth blogging about. Two things about forms in Rails:

1) You can’t nest them within a table. Let’s say you have this bit of code in your ERB:

<tr>
  <%= form_for TestClass.new do |f| %>
    <td>
      <%= f.text_field :test_field %>
    </td>
    <td>
      <%= f.submit 'Create' %>
    </td> 
  <% end %>
</tr>

What this results in is this:

<tr>
  <form action='/test_class'></form>
  <td>
    <input name='test_class[test_field]' type='text'>
  </td>
  <td>
    <input value='Create' type='submit'>
  </td>
</tr>

The form ends up closing before it actually ends, which means that it won’t actually submit properly. Bizarrely enough, sometimes it works… but it won’t work consistently. Lesson: don’t nest forms in tables. Haven’t tried it, but there’s a possibility that with HTML5, if you define the form outside of the <table&gth; element, then it will work.

2) You cannot instantiate a form in one div and then end it in another. This may seem obvious, but I see this a lot, especially with juniors. Example:

<div>
  <%= form_for TestClass.new do |f| %>
    <%= f.text_field :test_field %>
</div>
<div>
  <%= f.text_field :num_ponies %>
  <%= f.submit 'Create' %>
<% end %>
</div>

Results in this:

<div>
  <form action='/test_class'></form>
  <input name='test_class[test_field]' type='text'>
</div>
<div>
  <input name='test_class[num_ponies]' type='text'>
  <input value='Create' type='submit'>
</div>

No bueno. Never nest anything across multiple elements. HTML does not appreciate it.