Default Reference Values

[Mark Hawkes <ha...@onetel.com>]

In Perl, using HTML::Template, I can specify a default value in case the 
template variable remains unassigned, like so:

   <h1><tmpl_var name="greeting" default="hello"></h1>

How can I emulate this in VTL, so that if there's no value for 
"greeting" in the context it displays "hello" instead of just "$greeting"...

   <h1>$greeting</h1>

Many TIA,
Marco

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Re: Default Reference Values

[Simon Christian <si...@stoutstick.com>]

Hi Marco,

There are two simple ways to do this: using a macro or a tool that does 
the same job e.g.

#* macro example *#

// define the macro
// you may want to play with this depending on whether you would accept
// an empty string as the value
#macro( valueOrDefault $_value $_default )
#if( $_value ) $_value #else $_default #end
#end

#valueOrDefault( $greeting "hello" )


#* tool example *#

// create a tool class
public class MyTool
{
   public String valueOrDefault( String value, String default )
   {
     // this behaviour is slightly different to the macro as it
     // won't accept the empty string
     if( value != null && value.length() > 0 )
     {
       return value;
     }
     else if( default != null && default.length() > 0  )
     {
       return default;
     }
     else
     {
       return null;
     }
   }
}

// put it into your context somewhere
ctx.put( "mytool", new MyTool() );

// and use it
$mytool.valueOrDefault( "$greeting", "hello" )

Personally I prefer the macro..

hth,

- simon


Mark Hawkes wrote:
> In Perl, using HTML::Template, I can specify a default value in case the 
> template variable remains unassigned, like so:
> 
>   <h1><tmpl_var name="greeting" default="hello"></h1>
> 
> How can I emulate this in VTL, so that if there's no value for 
> "greeting" in the context it displays "hello" instead of just 
> "$greeting"...
> 
>   <h1>$greeting</h1>
> 
> Many TIA,
> Marco
> 
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: velocity-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: velocity-user-help@jakarta.apache.org
> 


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