Re: Velocity and evaluated symbol substitution

[Scott Eade]

Gerry Duprey wrote:

Howdy All,

I realize this is more a velocity question, but the velocity email 
list is shared with the jakarta commons list and doesn't seem to have 
much velocity traffic on it.

What I'm trying to do is create a velocity macro that can define an 
input field using a fixed name for the field and have that macro have 
provisions for default values for the field based on the fields fixed 
name.  For example, I'd love to do something like

#macro ( myInput $fieldName )
  <INPUT TYPE="TEXT" NAME="FLD_$fieldName" 
VALUE="$!{VALUE_${fieldName}}">
#end

so

#myInput ( "UserName" )

becomes

  <INPUT TYPE="TEXT" NAME="FLD_UserName" VALUE="Gerry">

Assuming my Context has a symbol called VALUE_UserName in it set to 
the string "Gerry" (i.e. context.put("VALUE_UserName", "Gerry")).

In short, the ability to have an interpreted reference/variable name.

It would also let me do things like having macros that knew how to 
display errors attached to fields automatically.  Consider:

#macro ( myInput $fieldName )
  <INPUT TYPE="TEXT" NAME="FLD_$fieldName" 
VALUE="$!{VALUE_${fieldName}}">
  #if ( ${ERROR_${fieldName}} )
    <FONT COLOR="red">* ${ERROR_${fieldName}}</FONT>
  #end
#end

This gives my verification routines a great deal of flexibility and 
allows very generic forms processing modules.

Any thoughts (on how to do this or if you think I'm bonkers, that is :-)?

Gerry

I would create a pull tool to provide the default values and error 
messages (much less cumbersome than David's suggestion) and then a 
velocity macro that uses the pull tool to produce the final result.

Scott

--
Scott Eade
Backstage Technologies Pty. Ltd.
http://www.backstagetech.com.au


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