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https://issues.apache.org/jira/browse/VELOCITY-692?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12673299#action_12673299
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Sergiy Kovalchuk commented on VELOCITY-692:
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I think it is pretty unexpected for a user. It basically means that you are not
allowed to use length() or isEmpty() methods in your objects for your needs. If
I have length or empty fields returning false or null or " ", it doesn't
necessary mean that the whole object should be treated as null or empty. Plus
"length" and "empty" are pretty common names, nobody expects that they will
become reserved one day for checking if the whole object is empty. Lets say I
have Rectangle object with "height" and "length" fields, or Train object with
isEmpty method, it doesn't mean that rectangle with length not set or train
that is not loaded are equal to null (maybe not the best examples, but you got
the idea)
Even returning false if obj.toString()==null (not to mention length==0) caught
me by surprise. I never thought that it is doing this check until saw it in the
code. What if I have toString method returning only one field of an object that
can be null or ""? I would spend a lot of time trying to figure out why does
this object is treated as null in #if statements. At least such behavior should
be noted in documentation with big red letters, because it is pretty unexpected
I think. toString() should be used however you want and nobody else should rely
on it in my opinion.
I think much safer would be just to check specifically CharSequence,
Collection, Map, array (anything else?) for their length/size.
> 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, <[email protected]> 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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