Embedding Ruby in html
So far we've looked at using Ruby to create HTML output, but we can turn the problem inside out; we can actually embed Ruby in an HTML document.
There are a number of packages that allow you to embed Ruby statements in some other sort of a document, especially in an HTML page. Generically, this is known as ``eRuby.'' Specifically, there are several different implementations of eRuby, including erubyanderb. The remainder of this section will discusseruby, written by Shugo Maeda.
Embedding Ruby in HTML is a very powerful concept---it basically gives us the equivalent of a tool such as ASP, JSP, or PHP, but with the full power of Ruby.
Using eruby
erubyacts as a filter, plain and simple. Any text within the input file is passed through untouched, with the following exceptions:
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Expression |
Description |
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<%ruby code%> |
The Ruby code between the delimiters is replaced with its output. |
|
<%=ruby expression%> |
The Ruby expression between the delimiters is replaced with its value. |
|
<%#ruby code%> |
The Ruby code between the delimiters is ignored (useful for testing). |
|
| |
You invoke erubyas:
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eruby [ options ][ document ] |
If the documentis omitted,erubywill read from standard input. The command-line options forerubyare shown in Table 14.1 on page 149.
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Command-line options for eruby
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Let's look at some simple examples. We'll run the erubyexecutable on the following input.
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This text is <% a = 100; puts "#{a}% Live!" %> |
erubysubstitutes the expression between the delimiters and produces
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This text is 100% Live! |
Using the <%= form acts as if you printed the value of the expression. For instance, the input
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<%a = 100%>This text is almost <%=a%> degrees! Cool! |
replaces the =awith the value ofa.
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This text is almost 100 degrees! Cool! |
And, of course, you can embed Ruby within a more complex document type, such as HTML.
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> <html> <head> <title>eruby example</title> </head> <body> <h1>Enumeration</h1> <ul> <%(1..10).each do|i|%> <li>number <%=i%></li> <%end%> </ul> <h1>Environment variables</h1> <table> <%ENV.keys.sort.each do |key|%> <tr> <th><%=key%></th><td><%=ENV[key]%></td> </tr> <%end%> </table> </body> </html> |