Block comments in html.erb templates in rails

Question

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).

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

Thanks!

Solution 1

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.

Solution 2

Use this for commenting single lines:

<%# your_ruby_code %>

For multiple lines, the

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

What you said would work.

Solution 3

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.

Solution 4

<%#=

...commented
multiline
block...

%>

Solution 5

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 ... 
  # %>

View more solutions

Comments

[Nikita Rybak]

1) you're right, jsp comments have slightly different format, I updated the post. 2) I can't find anything like that in IDEA or Netbeans. Did you have anything any particular IDE in mind saying this?

[Nikita Rybak]

I know it would, I'm interested if there's anything simpler :)

[John Topley]

No I didn't. Personally, I don't use an IDE for Rails projects.

[Garfield]

=begin I think the begin - end would be all =end # You may ignore my comment as its entirely commented :P

[dionyziz]

As far as I understand, he's looking for a multiline comment-out solution: If I have a block of n lines, I just want to be able to add a line at the top and the bottom (or maybe a couple) and have it work. I don't want to have to edit the whole block.

[dhaval]

it works if = is at start of new line just like in the answer

[Mariano Cavallo]

You can even write it as <% comment do %>...<% comment end %>. I've added this syntax to sublime text so that It even looks like a real comment.

[BenKoshy]

what if it is like this <%= %> ? Where would the hash go - before or after the equals sign?

[Adamantish]

Yes, but this still won't comment out both the HTML and the ruby.

[iono]

Hmm... sounds like good cause for a custom plugin. Maybe as a stopgap, you could press ctrl+d to multi-select the start of every Erb tag <% within the block and then hit ctrl+shift+/, then hit it once more for the whole block to comment out the HTML.

[Hovis Biddle]

This doesn't work. Any ruby tags inside the block comment will close the outer block.

[max]

You might as well just add a #... instead of sending ruby in the document.

[ViggoV]

Oops, tried to add a comment with multiline code. Will post an answer instead.

[Kieran Andrews]

I am getting this error: "embedded document meets end of file"

[Ulysse BN]

This answer should have way more interest.

[tanius]

Lovely solution!! One improvement: commenting code to disable it is kind of a hack, so rather call the method ignore or disable and we get a fully semantic solution: <% ignore do %>…<% end %>

[jamesc]

@Chloe Not quite sure why you directed your comment to me but you are quite correct <%= false %> would not work. You should try the solution provided though which would work <% if false %> without the = sign

[Chloe]

@jamesc Your comment was deleted before you saw my response. Someone deleted your comment where you said to use <%# if false %>.

[prashant]

As of Rails 6 at least, only the first # seems to be necessary.

[prashant]

As of Rails 6 at least, the = doesn't seem to be necessary.

[stevec]

I tried exactly that but with <% and =begin %> on the same line, which is much more intuitive. Why doesn't that approach work?

[Mithun Nair]

But this wont work when there is ERB code in one of the lines..For Ex

[stevec]

The commented block doesn't show grey colour in Sublime Text.