HTML Generation (Next Generation CGI)

Discussion in 'Ruby' started by John W. Long, Nov 22, 2003.

  1. John W. Long

    John W. Long Guest

    Hi,

    This idea for the next generation of CGI has me thinking (see
    http://rubygarden.org/ruby?NextGenerationCGI). It seems that CGI would be
    best if it were broken in two. One side handled generating html, and the
    other handled all the other stuff (params, headers, etc...).

    Last night I started prototyping some of my ideas and came up with the
    following:

    class HtmlGenerator
    def render(klass, &blk)
    hg = klass.new
    hg.render(&blk)
    end
    end
    class Html4
    attr_accessor :encoding
    def render(&blk)
    "<html>#{self.instance_eval(&blk)}\n</html>"
    end
    def head(&blk)
    "\n<head>#{self.instance_eval(&blk)}\n</head>"
    end
    def title(&blk)
    "\n<title>#{self.instance_eval(&blk)}</title>"
    end
    def meta(hash = {})
    "\n" + '<meta name="' + hash[:name] + '" content="' + hash[:content] +
    '">'
    end
    def body(&blk)
    "\n<body>#{self.instance_eval(&blk)}\n</body>"
    end
    def h1(&blk)
    "\n<h1>#{self.instance_eval(&blk)}</h1>"
    end
    def h2(&blk)
    "\n<h2>#{self.instance_eval(&blk)}</h2>"
    end
    def p(&blk)
    "\n<p>#{self.instance_eval(&blk)}</p>"
    end
    def b(&blk)
    "<b>#{self.instance_eval(&blk)}</b>"
    end
    def i(&blk)
    "<i>#{self.instance_eval(&blk)}</i>"
    end
    end

    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" } }
    }
    }

    I like the syntax of this very much, but I would like input on two things.

    The first this would require heavy use of instance_eval. Would this be a
    good thing? It strikes me that the main problem with instance_eval is that
    you can begin to change the interface of the class. However, as this is
    implemented above you can see that changes to the implementation would only
    effect an instance of the HtmlXX class, which would go into never never land
    as soon as the render call is completed.

    The second, a bit harder, I would like to remove the need for the pluses in
    order to chain the results together. Any Ruby gurus that would like to try
    and take a stab at it? I can think of one possible solution, but I'm not
    sure if the results would really be satisfactory.

    --
    John Long
    contact me through: www.wiseheartdesign.com
     
    John W. Long, Nov 22, 2003
    #1
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  2. 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" } }
    > }
    > }


    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.

    --
    _ _
    | |__ __ _| |_ ___ _ __ ___ __ _ _ __
    | '_ \ / _` | __/ __| '_ ` _ \ / _` | '_ \
    | |_) | (_| | |_\__ \ | | | | | (_| | | | |
    |_.__/ \__,_|\__|___/_| |_| |_|\__,_|_| |_|
    Running Debian GNU/Linux Sid (unstable)
    batsman dot geo at yahoo dot com

    Are Linux users lemmings collectively jumping off of the cliff of
    reliable, well-engineered commercial software?
    -- Matt Welsh
     
    Mauricio Fernández, Nov 23, 2003
    #2
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  3. John W. Long

    Ara.T.Howard Guest

    On Sun, 23 Nov 2003, Mauricio Fernández wrote:

    > Date: Sun, 23 Nov 2003 18:19:56 +0900
    > From: Mauricio Fernández <>
    > 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
    --

    ATTN: please update your address books with address below!

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    |
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    |
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    ===============================================================================
     
    Ara.T.Howard, Nov 23, 2003
    #3
  4. John W. Long

    John W. Long Guest

    > You can use a technique similar to flgr's Junction or oGMo's criteria to
    build a
    > "parse tree".


    I'm not familiar with either library. How would you see a parse tree helping
    in this situation?

    > 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.


    Honestly I don't think it would be that hard to do. The hairiness of the
    project would be understanding the finer points of dtd. Simply creating a
    generator object with a smart method_missing shouldn't be that hard. This
    object could then recursively create other generator objects that contain
    the appropriate subset of the dtd for the section of the document you are
    working on.

    --
    John Long
    http://wiseheartdesign.com
     
    John W. Long, Nov 24, 2003
    #4
  5. John W. Long

    John W. Long Guest

    > -- Ara Howard wrote: --
    > what advantage would this give over:

    <snip amrita stuff here />

    Actually I have used Amrita. And yes Amrita is a good library. I think it
    will be even better after it gets some of the kinks worked out of it. (Maybe
    it already has. I last looked at Amrita in the spring.)

    I'm not so interested in creating a template library. CGI currently has the
    kind of functionality I suggested. Personally I'm not sure I would
    personally use it, but it does meet another need. It can generate HTML code
    in several different flavors. From HTML3 - XHTML transitional if I remember
    right. This is kind of a neat idea, although as I said I'm not totally sure
    I would use it myself.

    --
    John Long
    http://wiseheartdesign.com
     
    John W. Long, Nov 24, 2003
    #5
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