Haml
Haml is a templating engine for HTML. It’s designed to make it both easier and more pleasant to write HTML documents, by eliminating redundancy, reflecting the underlying structure that the document represents, and providing an elegant syntax that’s both powerful and easy to understand.
Using Haml with Rails
To use Haml with Rails, simply add Haml to your Gemfile and run bundle.
gem 'haml'
If you’d like to replace Rails’s ERB-based generators with Haml, add haml-rails to your Gemfile as well.
Formatting
The most basic element of Haml is a shorthand for creating HTML:
%tagname{:attr1 => 'value1', :attr2 => 'value2'} Contents
No end-tag is needed; Haml handles that automatically. If you prefer HTML-style attributes, you can also use:
%tagname(attr1='value1' attr2='value2') Contents
Adding class and id attributes is even easier. Haml uses the same syntax as
the CSS that styles the document:
%tagname#id.class
In fact, when you’re using the <div> tag, it becomes even easier. Because
<div> is such a common element, a tag without a name defaults to a div. So
#foo Hello!
becomes
<div id='foo'>Hello!</div>
Haml uses indentation to bring the individual elements to represent the HTML structure. A tag’s children are indented beneath than the parent tag. Again, a closing tag is automatically added. For example:
%ul
%li Salt
%li Pepper
becomes:
<ul>
<li>Salt</li>
<li>Pepper</li>
</ul>
You can also put plain text as a child of an element:
%p
Hello,
World!
It’s also possible to embed Ruby code into Haml documents. An equals sign, =,
will output the result of the code. A hyphen, -, will run the code but not
output the result. You can even use control statements like if and while:
%p
Date/Time:
- now = DateTime.now
%strong= now
- if now > DateTime.parse("December 31, 2006")
= "Happy new " + "year!"
Haml provides far more tools than those presented here. Check out the reference documentation for full details.
Indentation
Haml’s indentation can be made up of one or more tabs or spaces. However, indentation must be consistent within a given document. Hard tabs and spaces can’t be mixed, and the same number of tabs or spaces must be used throughout.
Team
Current Maintainers
Alumni
Haml was created by Hampton Catlin, the author of the original implementation. Hampton is no longer involved in day-to-day coding, but still consults on language issues.
Natalie Weizenbaum was for many years the primary developer and architect of the “modern” Ruby implementation of Haml.
Norman Clarke was the primary maintainer of Haml from 2012 to 2016.