From: "Ara.T.Howard" <ahoward@...>
Date: 2003-11-24T04:02:18+09:00
Subject: Re: HTML Generation (Next Generation CGI)

On Sun, 23 Nov 2003, Mauricio Fern�ndez wrote:

> Date: Sun, 23 Nov 2003 18:19:56 +0900
> From: Mauricio Fern�ndez <batsman.geo@yahoo.com>
> Newsgroups: comp.lang.ruby
> Subject: Re: HTML Generation (Next Generation CGI)
> 
> On Sun, Nov 23, 2003 at 01:50:29AM +0900, John W. Long wrote:
> > Last night I started prototyping some of my ideas and came up with the
> > following:
> [...]
> > hg = HtmlGenerator.new
> > puts hg.render(Html4) {
> >  encoding = "US/English"
> >  head {
> >   title { "My Document" } +
> >   meta(:name => "description", :content => "this is a description of this
> > document")
> >  } +
> >  body {
> >   h1 { "Heading 1" } +
> >   p { "A small paragraph." } +
> >   h2 { "Heading 2" } +
> >   p { b { "Bold" } + " " + i { "Italic" } }
> >  }
> > }

what advantage would this give over:

~ > cat bar.rb
  require 'amrita/template'

  template = Amrita::TemplateText.new <<-html
  <html>
    <head><title id=title></title><meta id=meta/></head>
    <body>
      <h1 id=h1></h1> <p></p> <h2 id=h2></h2>
      <p> <b id=b></b> <i id=i></i> </p>
    </body>
  </html>
  html

  data = Hash[
    :title => 'My Document',
    :meta  => Amrita::a(:name => 'description'){'this is a description of this document'},
    :h1    => 'Heading 1',
    :p     => 'A small paragraph',
    :h2    => 'Heading 2',
    :b     => 'Bold',
    :i     => 'Italic',
  ]
  template.expand STDOUT, data

~ > ruby bar.rb
  <html>
    <head><title>My Document</title><meta></head>
    <body>
      <h1>Heading 1</h1> <p></p> <h2>Heading 2</h2>
      <p> <b>Bold</b> <i>Italic</i> </p>
    </body>
  </html>

> You can use a technique similar to flgr's Junction or oGMo's criteria to build a
> "parse tree".
> 
> What would be really cool would be taking a DTD and generating the Ruby
> code from that that validates the document as it is built.
> It would be possible to define how blocks can be nested, etc, in
> practice, ensuring that no illegal sequence of calls is made.

~ > cat foo.rb

  require 'amrita/template'
  template = Amrita::TemplateText.new <<-html
    <table>
      <b>
        <tr id=row><td id=a/><td id=b/></tr>
      </b>
    </table>
  html
  data = Hash.new[ :row => {:a => 'illegal', :b => 'row'} ]
  template.expand STDOUT, data

~ > ruby foo.rb

  /data/ruby-1.8.0//lib/ruby/site_ruby/1.8/amrita/parser.rb:304:in `parse': error hapend in :2(<tr> can't be in <b>)  (Amrita::HtmlParseError)

  ==>><td id=a/><td id=b/></tr>
      </b>
    </table>
          from /data/ruby-1.8.0//lib/ruby/site_ruby/1.8/amrita/parser.rb:269:in `parse_text'
          from /data/ruby-1.8.0//lib/ruby/site_ruby/1.8/amrita/template.rb:405:in `load_template'
          from /data/ruby-1.8.0//lib/ruby/site_ruby/1.8/amrita/template.rb:208:in `setup_template'
          from /data/ruby-1.8.0//lib/ruby/site_ruby/1.8/amrita/template.rb:115:in `expand'
          from foo.rb:10



amrita is pretty hard to beat.  at the very lest, it could be built on.  it's
handling of array's make generating complex pages very easy:

~ > cat foobar.rb
  require 'amrita/template'
  template = Amrita::TemplateText.new <<-html
  <html>
    <body>
      <table>
        <tr id=rows><td id=name></td><td id=ssn></td></tr>
      </table>
    </body>
  </html>
  html

  data = Hash[
    :rows => [
      {:name => 'joe', :ssn => '574-86-3205'},
      {:name => 'bob', :ssn => '572-84-8964'},
      # imagine there are _many_ of these
    ]
  ]
  template.expand STDOUT, data

~ > ruby foobar.rb
  <html>
    <body>
      <table>
        <tr><td>joe</td><td>574-86-3205</td></tr><tr><td>bob</td><td>572-84-8964</td></tr>
      </table>
    </body>
  </html>
 

it will hard to beat amrita's handling of nested data structures.  another
thing that is really good about it is that it separated html from cgi logic.
that way to can say "don't like how it looks?, here's the template - add
something" to your web designers.

anyhow, amrita is worth checking out.

-a
-- 

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