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Tuesday, 6 June 2017

基于rubygem的抽象标记语言-Haml

HTML Abstraction Markup Language - A Markup Haiku

Gem Version Build Status Code Climate Coverage Status Inline docs
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.

Basic Usage

Haml can be used from the command line or as part of a Ruby web framework. The first step is to install the gem:
gem install haml
After you write some Haml, you can run
haml document.haml
to compile it to HTML. For more information on these commands, check out
haml --help
To use Haml programatically, check out the YARD documentation.

Using Haml with Rails

To use Haml with Rails, simply add Haml to your Gemfile and run bundle.
gem 'haml'
Haml 5 will require Rails version 4.0 or later. If you are using Rails 3.x, you should use Haml version 4.0.x:
gem 'haml', '~> 4.0.5'
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.

from  https://github.com/haml/haml

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