From: "John W. Long" <ng@...>
Date: 2005-01-22T13:56:22+09:00
Subject: Unnamed::Template

I've been working on a yet-to-be-named templating system similar to in 
fashion to textpattern's (http://textpattern.org).

--

#Currently you can define a template:

   template = <<-TEMPLATE
     <jwl:cart>
     <ul>
     <jwl:item limit="5">
       <li><jwl:name /> <jwl:price /></li>
     </txp:item>
     </ul>
     Total: <jwl:total />
     </jwl:cart>
   TEMPLATE

#Define a Context class:

class CartContext < Template::Context
   def initalize
     @cart = Shopping::Cart.new
     @item = nil
   end

   def cart(attr)
     yield
   end

   def item(attr)
     result = ""
     @cart.items.each_with_index do |item, index|
       @item = item
       result << yield
       break unless attr["limit"] && (index < attr["limit"](
     end
     result
   end

   def name(attr)
     @item.name if @item
   end

   def price(attr)
     @item.price if @item
   end

   def total(attr)
     @cart.total
   end
end

#Then merge context with template for the expected results:

parser = Template::Parser.new( :pre => "jwl", :context => CartContext )
puts parser.parse(template)

--

I would like to work out a way to force tags to comply to a certain 
hierarchy. In this instance, you shouldn't be able to use the "item" tag 
out side of a "cart", or "name" or "price" out side of "item".

My current thought is to use a couple of class methods to make this work:

--

my_context = Context.new do
   tag "cart" do
     tag "item" do
       tag "name"
       def name(attr)
         @item.name if @item
       end
       tag "price"
       def price(attr)
         @item.price if @item
       end
     end
     def item(attr)
       result = ""
       @cart.items.each_with_index do |item, index|
         @item = item
         result << yield
         break unless index < attr["limit"]
       end
       result
     end		
   end
   def cart(attr)
     yeild
   end
end

--

The flaw of this implementation is that there is a fair amount of 
duplication. Does anybody have a better idea for a pseudo language for 
defining tag heirarchy?

You can find a version of the project attached to this message:

http://rubyforge.org/pipermail/chicagogroup-members-list/2005-January/000039.html

--
John Long
http://wiseheartdesign.com