Block comments in html.erb templates in rails

How do you comment out html mixed with ruby code?

some text <% ... %> more text <%= ... %>
something else
<% ... %>

In jsp it's real simple: <%-- ... --%>, but I'm unable to find any concise option in rails.

Simple html comments <!-- ... --> do not work: ruby code is still executed and yells errors.

There's an option to use if false with html comments, but it's quite verbose, not to mention IDEs doesn't support it.

There's also an option coming from pure ruby, which surprisingly works.

<%
=begin %>
... html and ruby code goes here
<%
=end %>

It's generally fine, except that it's verbose, weird-looking and none of ruby IDEs I know support it (yep, I like to comment/comment-out with one keystroke).

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I'm curious, is there any 'official' of doing this in rails?

Thanks!

---

Use this for commenting single lines:

<%# your_ruby_code %>

For multiple lines, the following would work:

<% =begin %>  
<% ruby_code %>
<% =end %>

What you said would work.

---

I wouldn't count as a solution, but perhaps enclosing the chunk between an

<% if false %>
   ...
<% end %>

or if you feel a little dirty, create a helper that simply outputs nothing.

I've never needed it, but I'm stumbled there seems to be no out-of-the-box solution for this.

---

The =begin approach is annoying because:

1. It doesn't work for mixed HTML and Ruby (or just HTML) that's on a single line
2. It's annoying to type

The <% if false %> approach works, but it looks weird and doesn't give anyone else who looks at your code a hint about your intentions.

My solution is as follows:

In application_helper.rb, add a method so:

def comment
end

Then in your view template, you can say:

<% comment do %>Some stuff that won't be rendered...<% end %>

This works because any Ruby method can take a block, but will silently ignore the passed-in block if your method doesn't include a yield.

---

<%#=

...commented
multiline
block...

%>

---

For block comments in templates, my text editor (Komodo) finds this variation on @Garfield's recommendation least obnoxious:

<%# A long multiline comment in a rails template ...
  # line 2
  # and so on ... 
  # %>

---

To comment out erb tags use the ruby comment hash symbol before the = sign in the opening tag

<p>
 This is some text I want to keep
 <%= @some_object.some_attribute %>
</p>
<p>
  I want to keep this text but comment out the erb tag
  <%#= @some_object.another_attribute %>
</p>
<!--
<p>
  I want all of this text commented out including the erb tag
  <%#= @some_object.some_attribute %>
</p>
-->
<!--
<p>
 I just want this html commented out but I want to keep the erb tag
 <%= @some_object.some_attribute %>
</p>
-->

---

Since you can use <% %> to put a ruby block, it can be certainly used to put in comments into it.

A simpler and elegant solution would look like...

<%
# See! I am a Ruby Comment
# And I am multi-line
# I look like a recognizable ruby comment block too
# and not so complex
# The only drawback with me is the Hash symbol you have to repeat
# But it's the norm, isn't it?
%>

---

After =begin you do not need to put %>

<%
=begin

code code code code code code 
code code code code code code 
code code code code code code 
code code code code code code 

=end %>

---

Just an addendum to some of the previous answers. I found the =begin/=end solution most useful, but for the sake of beauty I write it like so:

<%
=begin
  <p>HTML will be ignored</p>
  <%= 'and so will ruby' %>
  <p>
    <%= 'plus the whole block will be greyed in editor' %>
  </p>
=end
%>

Note that since everything is ignored until the =end there is no need to close the =begin tag with %> or open the =end tag with <% (which has also been pointed out in an earlier answer)

I found this to be the most elegant solution to completely outcomment a block of mixed ruby and html code and have it greyed out in my editor as well, as opposed to the <% if false %> solution. Only drawback is that =begin and =end must be placed at the very beginning of the line..

---

Use a HEREDOC called comment

Pros:

• Self-explanatory that this is a comment
• Works for erb and HTML tags
• Has ok syntax highlighting (as one long string)

Cons:

• Weird 3 line closing syntax
• No keyboard shortcuts

Code:

The opening tag can be

<% <<-COMMENT %>

the above closing erb tag is just for looks (to match the end),
but don't put anything else there, it may show up on the page

or

<%
<<-COMMENT
%>

Anything here won't run or show up in the browser

<P>
    this will not be displayed in the browser
    <strong> even in the developer's tools </strong>
</p>

<% 1_000_000_000_000.times do |count| %>

for the <%= count %>'th time, this won't run a trillion times,
this is all just a string

all of these %>, <%, <% end %>, end, do, <!--, won't cause any issues.

but the below opening erb tag is important (if you used any erb tags in the comment).
I have no clue why?

The closing tag

yes it needs to be 3 lines