Use of <%= %> instead of <% %> ruby on rails

Question

I've been following Agile Web Development with Rails, and their code suddenly switches from the use of <%= %> to <% %>.

Code Example 1:

<%= 1+2 %>

Code Example 2:

<% for file in @files %>    
file name is: <%= file %>
<% end %>

My question is, for the second code sample why can I not use <%= %>?

Thanks!

No worries. Common question, hard to search for. Bound to happen. — gwcoffey, Jun 02 '14 at 02:55

score 3 · Accepted Answer · answered Jun 02 '14 at 02:39

In ERB (embedded ruby) syntax, <%= %> is shorthand for "perform the following ruby code AND THEN print the result". So in the first example, it will print the result of the operation 1 + 2, 3.

The second example shows a for loop which will iterate and print the contents between the for declaration and its corresponding <% end %>.

To answer your question, the expression for file in @files itself doesn't return anything worth printing so there's no need to use <%= %> and in fact doing so can cause a hard-to-track-down bug.

Best way to think about it is `<%=` is the equivalent of `echo` in PHP. So `<%=` == `<$ echo` — Richard Peck, Jun 02 '14 at 07:10

Use of <%= %> instead of <% %> ruby on rails

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