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From "Nathan Bubna (JIRA)" <...@velocity.apache.org>
Subject [jira] Commented: (VELOCITY-692) have #if handle empty strings/arrays/collections/maps more conveniently
Date Fri, 13 Feb 2009 22:02:59 GMT

    [ https://issues.apache.org/jira/browse/VELOCITY-692?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12673393#action_12673393
] 

Nathan Bubna commented on VELOCITY-692:
---------------------------------------

Sorry, hit submit prematurely.  To finish that last paragraph... 

The syntax differentiates the operation.  There is no need for a separate directive.  At that
point, we should just forget it and leave people to do #if( $foo.isEmpty() ), rather than
do it for them.

And yes, it is true there would be a backwards compatibility issue, but it is relatively small.
 I don't expect many people are (or should be) relying upon #if( $foo ) to distinguish empty
lists/strings from non-empty ones.  But we would certainly have to make this clear in the
changelog and documentation.

And yes, $null is just a regular variable, albeit with the benefit of (approximately) never
being defined, as people don't tend to refer to actual objects with the key "null".  They
could, but that would be stupid. :)

> have #if handle empty strings/arrays/collections/maps more conveniently
> -----------------------------------------------------------------------
>
>                 Key: VELOCITY-692
>                 URL: https://issues.apache.org/jira/browse/VELOCITY-692
>             Project: Velocity
>          Issue Type: New Feature
>          Components: Engine
>            Reporter: Nathan Bubna
>            Priority: Trivial
>
> An idea from the dev list:
> -------------------------------------------------------------------------------------------------
> On Sat, Feb 7, 2009 at 3:41 PM,  <serg472@gmail.com> wrote:
> > Hello,
> > I wanted to share with you a few ideas I have about new simple
> > improvements for DisplayTools. I should be able to make patches for
> > them if you are interested.
> >
> > 1. Add new method
> >
> > isEmpty(object)
> >
> > that will return true if the object is null or empty (for strings it's
> > zero length; for collections, maps and arrays it's zero size). This
> > should help with  annoying null checks. (Probably a better place for
> > this method would be Engine, not Tools)
> yeah, not something for tools.  would be interesting to have the
> Uberspect pretend that every non-null reference has an isEmpty()
> method, or perhaps just add 0-length strings, empty collections, empty
> maps and 0-length arrays to the list of things that #if( $foo )
> considers false.
> -------------------------------------------------------------------------------------------------

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