Re: Expression Handling Again

Rather than creating a StringMacro, create a StringTemplate, with a  
mini-template of:
     #set $foo = $x + 1

Then use a custom TemplateVisitor to pull out the "SetValue" argument  
of the #set directive:

     static class MyTemplateVisitor extends TemplateVisitor {
         Object value;

         public Object getValue() {
             return value;
         }

         public void visitDirectiveArg(String string, Object object) {
             // the #set directive has 2 arguments:  "SetTarget" (LHS)
             // and "SetValue" (RHS).  We're only interested in  
"SetValue"
             if (string.equals("SetValue")) {
                 value = object;
             }
         }
     }

So, you're code will be something like:

public Object evalExpression (Context context, String expression) {
     StringTemplate tmpl =  new StringTemplate (context.getBroker(),  
"#set $foo = " + expression);
     MyTemplateVisitor visitor = new MyTemplateVisitor();

     template.parse();
     template.accept(visitor);

     Object value = visitor.getValue();
     if (value instanceof Maco) {
         return ((Macro) value).evaluate(_context);
     } else {
         return value;
     }
}

Hope this helps.

eric





On Sep 22, 2005, at 12:22 PM, Dan Miller wrote:

> I guess what I was wondering about was using the api
> directly stepping in before the #set places the result
> into the context. I was looking into the src for
> PropertyMethod and trying to figure out how to get the
> result.
>
> I am using webmacro throughout a webproject, and would
> like to use similiar webmacro expression in xml files
> which are read and processed. Thanks
>
> --- Keats Kirsch <[email protected]> wrote:
>
>
>> AFAIK there are only two ways to get something out
>> of a WM template
>> expansion -- capture the result of the expansion, or
>> pull something from
>> the context.  Actually I suppose you could use the
>> #bean directive to
>> create a "global" variable and then get it from the
>> Broker.
>>
>> Maybe if you can explain your requirements we could
>> think of a way of
>> doing what you want.
>>
>> Keats
>>
>> Dan Miller wrote:
>>
>>
>>> The usage of the StringMacro to use the #set
>>>
>> directive
>>
>>> works great. I was wondering if there is anything
>>> exposed to evaluate the expression without
>>>
>> modifying
>>
>>> the context.
>>>
>>> This works great, but I would like to leave the
>>> context as is, not adding new temp variables to the
>>> context.
>>>
>>> Context ctx = new Context();
>>> ctx.put("val1", 1);
>>> ctx.put("val2", 155);
>>> Macro macro = null;
>>> macro = new StringMacro("#set $val = $val1 +
>>>
>> $val2");
>>
>>> macro.evaluate( ctx);
>>> Integer val = (Integer)ctx.get("val");
>>>
>>>
>>> I am looking forward to the 2.0 release.
>>>
>>>
>>>
>>
>>
>>
>>
>>
>>
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