Rails html.erb filetype, difference between <% %> and <%= %>

Question

I just began digging into Ruby and Ruby on Rails, and I noticed two options for embedding Ruby syntax within .html.erb files:

<% #ruby code here %>

Or:

<%= #ruby code here %>

How should I choose one over the other?

Thanks @DaveJohnston. I searched for similar questions based on the syntax, but I didn't see that post. — Stuart Kershaw, Nov 17 '13 at 22:37

Zach Latta · Accepted Answer · 2013-11-18T12:31:05.927

6

<%= outputs the result of the Ruby. <% just evaluates the Ruby.

<p>Hi! How are you? 1 + 1 = <%= 1 + 1 %></p>

Will become <p>Hi! How are you? 1 + 1 = 2</p>.

<p>Hi! How are you? 1 + 1 = <% 1 + 1 %></p>

Will become <p>Hi! How are you? 1 + 1 = </p>.

<% is generally used for flow control, ex. if/else. Example:

<% if model.nil? %>
  <%= render 'new_model_form' %>
<% else %>
  <%= render 'detail_view' %>
<% end %>

edited Nov 18 '13 at 12:31

answered Nov 17 '13 at 22:37

Zach Latta

Nice concise answer with examples. Much appreciated. – Stuart Kershaw Nov 17 '13 at 22:39
2

Well said. It might help only to add that <% is generally used for flow control like if/else, iterators, etc – AndyV Nov 18 '13 at 00:35

score 1 · Answer 2 · answered Nov 17 '13 at 22:35

1

<%= renders, <% does not.

answered Nov 17 '13 at 22:35

Jim Pedid

2 Answers2