[VELOCITY-600] #foreach & velocityCount

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.6
• Component/s: Engine
• Assignee: Unassigned
• Reporter: Adrian Tarau
• Created: 09/Jun/08 19:41
• Updated: 27/Dec/08 23:05
• Resolved: 15/Aug/08 19:33

Description

velocityCount = Used in the #foreach() directive, defines the string to be used as the context key for the loop count. A template would access the loop count as $velocityCount.

Knowing current version of the loop counter is very useful, but something is missing. Very often, when you generate some content base on a model(JavaScript code based on some UI model) you have the need to know if this is the last time when the #foreach block will be executed or not.

Example

You have a collection of objects Property(bean with key, value fields) and you want to generate a JavaScript object with them. The result should be like this :

{id : 1 , name = "John", ...}

you can generate this with

{
#foreach($property in $properties)
$property.key : "$property.value" #if($velocityCount != $properties.size()) , #end
#end
}

You can store $properties.size() of course outside the loop.

The template will be less verbose if I will have something like that. #if($velocityHasNext) , #end.

Instead of saving only the counter, a new variable called velocityHasNext whould be populated with the result of iterator.hasNext(). This is a minor modification of current #foreach directive

while (!maxNbrLoopsExceeded && i.hasNext())
{
// TODO: JDK 1.4+ -> valueOf()
context.localPut(counterName , new Integer(counter));
context.localPut(hasNextName , i.hasNext()); <--- here is the change
Object value = i.next();
context.localPut(elementKey, value);

/*

• If the value is null, use the special null holder context
  */
  if( value == null )
  Unknown macro: { if( nullHolderContext == null ) { // lazy instantiation nullHolderContext = new NullHolderContext(elementKey, context); } node.jjtGetChild(3).render(nullHolderContext, writer); }

  else

  { node.jjtGetChild(3).render(context, writer); }

  counter++;

// Determine whether we're allowed to continue looping.
// ASSUMPTION: counterInitialValue is not negative!
maxNbrLoopsExceeded = (counter - counterInitialValue) >= maxNbrLoops;
}

also init should contain

public void init(RuntimeServices rs, InternalContextAdapter context, Node node)
throws TemplateInitException

{ super.init(rs, context, node); counterName = rsvc.getString(RuntimeConstants.COUNTER_NAME); hasNextName = rsvc.getString(RuntimeConstants.HAS_NEXT_NAME); counterInitialValue = rsvc.getInt(RuntimeConstants.COUNTER_INITIAL_VALUE); .... }

This should help creating clear templates(and avoid some mistakes, sometime - like using the wrong collection to test ).

Thanks.

Issue Links

• relates to: VELOCITY-658 $velocityHasNext does not work in nested loops