Intro to Haml
13
HAML or, how to get <arrowheads> out of your face Presented by Clifford Heath
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Presentation on HAML given by Clifford Heath at the Melbourne Ruby group 2007/08/30.
Transcript of Intro to Haml
HAMLor, how to get <arrowheads> out of your face
Presented by Clifford Heath
Is THIS YOU?
when you see...<div id="column1" class= "robust"> <div class="sidebaritem"> <div class="sbihead"> <h1>Status Watch</h1> </div> <div class="sbicontent"> <%= render :partial => 'layouts/sidebar', :locals => { :value =>@mvalue } %> </div> </div> <div class="sidebaritem"> <div class="sbihead"> <h1>Your Account</h1> </div> <div class="sbilinks"> <ul> <% if session[:user_id] %> <li><%= link_to 'Log Out', :controller => 'authenticate', :action => 'logout' %></li> <% if @user && @user[:is_admin] -%> <li><%= link_to "Administration", :controller => 'admin', :action => 'index' %></li></etc></etc></etc> the right number of times ...
With HAML...
#column1.robust .sidebaritem .sbihead %h1 Status Watch .sbicontent = render :partial => 'layouts/sidebar', :locals => { :value =>@mvalue } .sidebaritem .sbihead %h1 Your Account .sbilinks %ul - if @user %li= link_to 'Log Out', :controller => 'authenticate', :action => 'logout' - if @user[:is_admin] %li= link_to "Administration", :controller => 'admin', :action => 'index'
What’s Changed?
All <arrowheads> are gone
Tags and code both self-close by indentation
id=”xyz” and class=”abc” are just #xyz and .abc
<div> is the default tag - for others, use %tag
<%= some code %> is now just = some code
Same for <% some code -%>, use - some code
Visual Simplicity
The RHTML version has 261 lexical tokens
counting each word in strings and syntactic white-space
The HAML version has 117 tokens
That makes it easier on the eyes and the fingers!
Markup Haiku
Read it again...
#column1.robust .sidebaritem .sbihead %h1 Status Watch .sbicontent = render :partial => 'layouts/sidebar', :locals => { :value =>@mvalue } .sidebaritem .sbihead %h1 Your Account .sbilinks %ul - if @user %li= link_to 'Log Out', :controller => 'authenticate', :action => 'logout' - if @user[:is_admin] %li= link_to "Administration", :controller => 'admin', :action => 'index'
Extra benefits
Need care to close tags correctly in RHTML
In HAML, generated code is indented properly
including after nesting layouts and partials!
valid XHTML with no extra effort
DIVs almost always get a class or an ID or both
Plays well with RHTML during conversion
Other niceties
Attribute values are Ruby code:%label{:for=>@field.name}= @field.description+’:’
Ruby blocks are automatically closed:%table - @people.each do |person| %tr %td= person.name%p.footer
You can declare multiple classes, etc:%td.person.alignleft#husband= @husband.name
Other niceties... 2
ID and class attributes can come from an object:%div[@mother]uses @mother.class and @mother.id to become:<div class=”person” id=”person_5724”>
Most self-closing tags are recognisedothers may be declared self-closed: %br/
Comments start with a single / and are output!Even multi-line; a comment wraps indented content
Other niceties... 3
Automatic generation of DOCTYPE tags:!!! and !!! XML become<?xml version="1.0" encoding="utf-8" ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
Continue a long line using a trailing |
:filter passes the content to the filter:%p :markdown Textile ======= Hello, *World*
Tools
Syntax highlighting modules available
JEdit, Eclipse + RadRails, TextMate, (G)Vim, Komodo, Emacs
or simple VIM setup (in your ~/.vimrc):
au BufRead,BufNewFile *.haml set sw=2 sts=2 et
How to install
./script/plugin install http://svn.hamptoncatlin.com/haml/tags/stable
Also available as a GEM for use outside Rails
Website: http://haml.hamptoncatlin.com/
See also SASS - similar approach for stylesheets
Developer discussion: http://groups.google.com/group/haml
Thanks to Hampton Catlin and his contributors!
