From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2001-10-29T12:40:35+09:00
Subject: [ruby-talk:23706] Re: Simple templating system (Oops... some bugs here)

In article <rz2D7.33566$TF4.1709731@sjcpnn01.usenetserver.com>,
Phil Tomson <ptkwt@shell1.aracnet.com> wrote:
>In article <Pine.LNX.4.30.0110280643200.9875-100000@candle.superlink.net>,
>David Alan Black  <dblack@candle.superlink.net> wrote:

Actually, there are a few problems here - that'll teach me to test more 
before posting ;-)
The main thing is that the #>IF #{condition} doesn't work right.
See comments below in the code:

>Here's the code I came up with to do this:
>
>#template.rb
>class String
>  def interpolate(bind)
>    eval (self.inspect,bind)
>  end
>end
>
>class TemplateFile
>   attr_reader :fileString
>   def initialize(file,bind)
>      @stateArray = Array.new
>      @stateArray << true #default read state
>      @fileString = ""
>      @bind = bind
>      File.foreach(file) {|line|
>        case line
>           when /^#>IF/
>              #check condition
>              condition = line.gsub(/#>IF/,"").strip
>              puts "condition is: "+condition if $DEBUG

The 'condition.interpolate(@bind)' below always returns a String with 
either "true" or "false" - not a TrueClass or FalseClass type....
I wonder why I can't eval the resulting string and get a TrueClass or 
FalseClass - it doesn't seem to work like that, though.

>              @stateArray << condition.interpolate(@bind)
>              puts "#{line} : #{@stateArray.to_s}" if $DEBUG
>           when /^#>ELSE/
>              #invert condition
>              @stateArray[-1] = !@stateArray[-1]
>           when /^#>END/
>              @stateArray.pop
>           when /^#>INCLUDE/
>              fields = line.split
>              file = fields[1].strip
>              puts "file to include is: #{file}"

....So the following tests will always come out true and will always be 
done even if the condition tested was false...

>              @fileString << include(fields[1].strip) if @stateArray.last
>           else @fileString << line if @stateArray.last
>        end
>      }
>   end
>
>   def include(file)
>      tf = TemplateFile.new(file,@bind)
>      tf.fileString
>   end
>
>   def interpolate(b=nil)
>      if b
>         @fileString.interpolate(b)
>      else
>         @fileString.interpolate(@bind)
>      end
>   end
>
>end
>
>if $0 == __FILE__
>   var = "string"
>   tf = TemplateFile.new("vhdl",binding)
>   #test different vector lengths:
>   5.times do |i|
>      puts "for #{i}:"
>      puts tf.interpolate(binding)
>   end
>end
>#end Template.rb
>
>
>BTW: the code in template.rb above also can handle some 'directives':

Another problem with the #>IF #{condition} is that if the condition has 
changed since the file was read (say the condition is: #{i>2} and now 
after the file was read, i has changed) it won't be reflected in the 
results. So this part is not currently working (the solution is to re-read 
the file everytime).

>#>IF #{condition}
>#>ELSE
>#>END
>

But this does work...
>#>INCLUDE <filename>  - reads in a specified file and includes it.

I'll fix these bugs and repost... maybe I'll put it on the RAA or 
cookbook.
Phil