Difference between -%> and %> in rails

Question

I have started some rails tutorials and noticed that some of the view code blocks are like

<h1><%= @subject.name -%></h1>

and other code blocks are like

<h1><%= @subject.name %></h1>

What is the difference between -%> and %>

If you know of some good syntax references you can point me to, that would also be helpful.

Answer 1

The extra dash makes ERB not output the newline after the closing tag. There's no difference in your example, but if you have something like this:

<div>
  <% if true -%>
  Hi
  <% end -%>
</div>

It'll produce:

<div>
  Hi
</div>

and not this:

<div>

  Hi

</div>

Answer 2

If you use HAML rather than ERB you can do something similar with a less than or greater symbol than after your tag.

> will remove any whitespace around your tag and < will remove any whitespace within it.

.float-left<
  %p
    Lorem ipsum dolor sit amet

is compiled to:

<div class="float-left"><p>
  Lorem ipsum dolor sit amet
</p></div>

And…

%left_tag
%inside>
%right_tag

is compiled to:

<left_tag /><inside /><right_tag />

If you're not using HAML it's definitely worth checking out.