Difference between <%= and <%"

Rails
#1

Hi all

what is the difference between <%= and <% in a view file?

thanks

#2

<%= prints the contents of the tag, whereas <% does not

#3

And you couldnt just try that out yourself? :smiley:

#4

On Aug 18, 2011, at 6:05 PM, 7stud – wrote:

rails

The <% tags just execute the ruby code and don’t enter any text onto
the
page, which causes ruby/.erb to loop over the

tag 3 times. The
<%= tag inside the loop prints the value of the variable i. So you
get:
loop: 0
loop: 1
loop: 2

Here’s another way to look at this. ‘<%=’ is a shortcut for ‘<% puts’.
There’s a similar construction in PHP: ‘<?=’ is a shortcut for ‘<?php
echo (or print)’.

Walter

#5

Thank you all for your answers!

#6

Tim S. wrote in post #1017353:

<%= prints the contents of the tag,

Well, it never meant that. <%= tells ruby to print the result of the
expression between the tags. For instance,

<%= 2+2 %>

would not print ‘2+2’, it would print ‘4’. But even the “result of
the expression” isn’t an entirely accurate description–because in rails
3 you write:

<%= form_for(@user) do |f| %>

which doesn’t fit that description. In ruby, ‘form_for(@user) do |f|’
isn’t an expression–it’s the first half of a loop/block, so it’s an
incomplete expression. In other words, in ruby if you wrote:

result = some_func(arg) do |x|

you would get an error. Maybe its best to think of <%= form_for() as an
exception to the rule?

One example of how <%= and <% differ is this:

<% 3.times do |i| %>

loop: <%= i %>
<% end %>

The <% tags just execute the ruby code and don’t enter any text onto the
page, which causes ruby/.erb to loop over the

tag 3 times. The
<%= tag inside the loop prints the value of the variable i. So you get:
loop: 0
loop: 1
loop: 2
#7

Walter D. wrote in post #1017505:

Here’s another way to look at this. ‘<%=’ is a shortcut for ‘<% puts’.
There’s a similar construction in PHP: ‘<?=’ is a shortcut for ‘<?php
echo (or print)’.

Walter

I do not believe you can use ‘<% puts’ in ERB, i thought you are
supposed to use ‘<% concat’

Alexey.

#8

On Aug 21, 2011, at 3:34 AM, Alexey M. wrote:

supposed to use ‘<% concat’
Thanks! I never tried this, actually.

Walter