yaml_and_haml.md

###Yaml and HAML

What is YAML and HAML?

What does YAML stand for??
YAML: YAML Ain't Markup Language (Yet Another Markup Language) it was changed to distinguish its purpose as data-oriented and rather than a document markup

• YAML was created to easily map data types such as lists and arrays.
• YAML is structured in a way that is easy for human to read, like an outline
• YAML doesn't use enclosures such as quotation marks, brackets, braces and open/close tags.
• spaces and indentations are not important as long as parallel elements have the same left justification and nested elements are indented further

receipt:     Oz-Ware Purchase Invoice
date:        2012-08-06
customer:
    given:   Dorothy
    family:  Gale

items:
    - part_no:   A4786
      descrip:   Water Bucket (Filled)
      price:     1.47
      quantity:  4

    - part_no:   E1628
      descrip:   High Heeled "Ruby" Slippers
      size:      8
      price:     100.27
      quantity:  1

• so how do you use YAML with Ruby?

- !ruby/object:Person 
  name: John Doe
  sname: jdoe
  email: jdoe@gmail.com
- !ruby/object:Person 
  name: Jane Doe
  sname: jdoe
  email: jane@hotmail.com

FILENAME = 'data.yaml'

class Person 
 attr_accessor :name, :sname, :email
end

require "yaml"
# Will return an array of Person objects.
data = YAML::load(File.open(FILENAME))

# Will print out the first object in the array's name. #=> John Doe
puts data.first.name ==> "John Doe"

What does HAML stand for?
HAML: HTML Abstraction Markup Language.
Haml believes that markup should be beautiful and it should accelerate and simplify template creation.

• to write a tag in HAML we use the percent sign %
• if you are writing ruby code, after the percent sign would come a = which ells HAML to evaluate Ruby code to the right and print out the return value as the contents of the tag, like erb tags <%= %>
• you add attributes such as class, ids in HAML like how you would write a hash {:class => 'code'}
• since classes and ids are so common you can actually just write %strong.code#message and haml will understand you
• since divs are so common, you can actually leave them off too
• Nesting in HAML is taking care of by whitespace, so indentation

<strong><%= item.title %></strong>
<strong class="code" id="message">Hello, World!</strong>

%strong= item.title
%strong{:class => "code", :id => "message"} Hello, World!
%strong.code#message Hello, World!

I think...I'm going to embrace HAML

<div id='content'>
  <div class='left column'>
    <h2>Welcome to our site!</h2>
    <p><%= print_information %></p>
  </div>
  <div class="right column">
    <%= render :partial => "sidebar" %>
  </div>
</div>

#content
  .left.column
    %h2 Welcome to our site!
    %p= print_information
  .right.column
    = render :partial => "sidebar"