Haml: how to generate dynamic id

Question

I've got following code in erb which works fine:

<div id='flash_<%= flash.keys.first.to_s %>'>
    <%=h    flash[flash.keys.first] %>
</div>

I want to convert it into haml:

#flash_#{flash.keys.first.to_s}
  =h flash[flash.keys.first]

But I receive error:

Illegal element: classes and ids must have values.

Which is strange as there IS value, 'flash_' part is always present, I get that error even when I do:

#flash_#{nil.object_id}

Apparently something wrong is with my Ruby interpolation in haml, but I can't get it right. According to documentation http://haml.info/docs/yardoc/file.REFERENCE.html#ruby_interpolation_ #{} is used to interpolate Ruby and it works in such case:

#flash_
  #{flash.keys.first.to_s}

but that's not what I want.

To sum up, I want to get the following output:

<div id="flash_foo"> blahblah </div>

but it can be also:

<div id="flash_"></div>

How to obtain that with haml?

Answer 1

%div{ :id => "flash_#{flash.keys.first}" }    
  =h flash[flash.keys.first]