{{lowercase}}
'''eRuby''' is a type of implementation that embeds [[Ruby programming language|Ruby]] into [[HTML]] or any other text document. Ruby code embedded in an HTML document, similar to [[Active Server Pages|ASP]], [[JavaServer Pages|JSP]] and [[PHP]], requires an interpreter to execute and replace it with designated HTML code and content.

There are several implementations of eRuby:

==Eruby==
'''eruby''' is an implementation of [[eRuby]], embedding [[Ruby programming language]] into any text-based document format, such as [[HTML]] or [[XML]]. By convention, an eRuby file ends with ''.rhtml'' [[file extension]], but this is certainly not a requirement.

eRuby allows Ruby code to be embedded within (delimited by) a pair of <code><%</code> and <code>%></code> delimiters. These embedded code blocks are then evaluated in-place (they are replaced by the result of their evaluation).

Here are a few examples of eRuby usage:

'''One Line of Ruby'''
<pre><% ruby code %></pre>

Output like hello from <code><% print "hello" %></code> would replace the ruby code between the delimiters.

'''Multiple Lines'''
These can appear less graceful because the beginning and ending are not quite the same. They function like blocks in Ruby and are terminated by <code><% end %></code>. They are commonly used as looping constructs, which appear like this:
<pre><ul>
<% 3.times do %>

<li>list item</li>

<% end %>
</ul>
</pre>

Outputting:
<ul>
<li>list item</li>
<li>list item</li>
<li>list item</li>
</ul>

If you come from other languages such as PHP or Perl, the structure may not seem intuitive, but is often very concise and readable (if you know Ruby, of course).

'''Expression Result Substitution'''
<pre><%= ruby expression %></pre> - Value evaluated from expression like 11 from <code>7 + 4</code> would replace the ruby expression between the delimiters. Often these are only one line.

'''Comments'''
<pre><%# ruby code %></pre> - this is the same as a comment in Ruby. All Ruby code after the # is ignored and generates nothing.

Other things common in eRuby are simply common in Ruby, such as string substitution with <pre>#{string_name}</pre> which is similar templating languages in Perl or PHP. The main difference could be described as "string_name" in Ruby is a string object, and not a string variable. In practice it works almost the same.

==Erb==
'''erb''' is an implementation of [[eRuby]], embedding the [[Ruby programming language]] into an [[HTML]] document. An eRuby file ends with ''.eruby'' [[file extension]]. In a popular implementation of eRuby in [[Ruby on Rails]], the file extension is ''.rhtml.''

==See also==
* [[Haml]]
* [[Markaby]]
* [[Master Templates]]
* [[Liquid]]

==External links==
* [http://ruby-doc.org/docs/ProgrammingRuby/html/web.html "Ruby and the web"], a chapter from [http://ruby-doc.org/docs/ProgrammingRuby/ "The Pragmatic Programmer's Guide"]
* [http://www.eruby.info/ www.eruby.info]
* [http://www.hiveminds.co.uk/node/3094 eRuby:How to Get Started with Ruby Web Programming]
* [http://www.hiveminds.co.uk/node/3098 eRuby:Using Ruby DBI for Database Connectivity]
* [http://www.hiveminds.co.uk/node/3100 eRuby:Getting Started with Ruby on Windows IIS]
* [http://www.hiveminds.co.uk/node/3096 eRuby: Using Ruby and MySQL for dynamic web pages]
* [http://www.hiveminds.co.uk/node/3093 eRuby: Using Embedded Ruby to Create Web Pages]

{{Ruby programming language}}
[[Category:Template engines|ERuby]]

[[ja:eRuby]]