Re: "addition" of lists

On 05/24/2013 02:37 PM, [email protected] wrote:
> Hey Sergiu! A big pleasure to meet you here! Thanks for your answer. Please, see below...
> 
>> ________________________________________
>> From: Sergiu Dumitriu [[email protected]]
>> Sent: 24 May 2013 19:54
>> To: [email protected]
>> Subject: Re: "addition" of lists
>>
>> On 05/24/2013 01:50 PM, [email protected] wrote:
>>> Hi!
>>>
>>> Probably I'll use the wrong semantic, but I'll try to explain the very simple result I want
>>> to get with Velocity: given two lists of results, let's me call them $list1 and $list2,
>>> I want to get a new list, let's call it $listTotal, including all item in $list1 and $list2.
>>>
>>> Please, how could I do that? What is the correct expression I must it in Velocity's World for his operation?
>>>
>>> Thank you so much for your help!
>>>
>>> Ricardo
>>>
>>
>> Hey Ricardo,
>>
>> If those are indeed lists, they should support all the methods that
>> Java's List class provides [1], including addAll [2], so this should work:
>>
>> #set ($listTotal = [])
>> #set ($discard = $listTotal.addAll($list1))
>> #set ($discard = $listTotal.addAll($list2))
>>
> 
> It worked! They are indeed lists :-) But I've not a clear idea yet about what is list, what an array, what a collection, what any sort of collection... Please, could you provide me a good reference to keep trying to understand what I feel like a must to leverage the power of Velocity and, of course, the nice team XWiki/Velocity?
> 
> These two lists come from a for you well known lines of code. Something like this...
> 
> #set ($xwqlquery = "where doc.translation = 0 and doc.creationDate < '2013-01-01' and doc.parent like '%$doc.title%' and doc.fullName NOT IN ($nicestr0) order by doc.object(XWiki.XWikiUsers).last_name")
> #set ($results = $services.query.xwql($xwqlquery).execute())
> 
> Please, is it possible to check $results if is it a list? For instance, I guessed it is a list because I can apply size() to it. Is this a right guess?

You can always check the actual class of a variable with:

$var.class

This will print the classname, which will correspond to a real Java
class (most likely an ArrayList).

You can then look up that class in your favorite Java IDE and look at
its hierarchy: which interfaces does it implement (List, Set or Map),
what methods does it have, etc.

One exception is that arrays (like String[]) are treated as lists by
Velocity, so they will also support all the List methods, even though in
Java they don't.

> Thank you so much for your help!
> 
>>
>> [1] http://docs.oracle.com/javase/1.5.0/docs/api/java/util/List.html
>> [2] http://docs.oracle.com/javase/1.5.0/docs/api/java/util/List.html#addAll%28java.util.Collection%29
> 
> Thanks!


-- 
Sergiu Dumitriu
http://purl.org/net/sergiu