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https://issues.apache.org/jira/browse/FREEMARKER-73?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16185094#comment-16185094
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Ondra Žižka commented on FREEMARKER-73:
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One more note for {{?sequence}}.
How would that handle non-existing variables, nulls and scalar types? Is there
any specification?
How about these:
""?seqence -> [""] ?
nonExistent?seqence -> [] ?
nonExistent!?seqence -> [] ? Would [""] make sense here?
false?sequence -> [] ? Or [false] ?
null?sequence -> [] ? Or null?
As a starting point here, I would take that scalar values would come before
{{?sequence}} mostly as a result of a missing value, a safeguard for it
({{!}}), a check for it, or a function returning something else than normally
(e.g. no items found -> null) etc.
Therefore, the resulting values should be the least surprise, i.e. I would
prefer [] in most places. Because then, the value is most likely going to be
used for {{<#list>}} or other way of iteration, and (not) iterating over an
empty sequence won't do any harm.
> ?seq to convert some models to a sequence
> -----------------------------------------
>
> Key: FREEMARKER-73
> URL: https://issues.apache.org/jira/browse/FREEMARKER-73
> Project: Apache Freemarker
> Issue Type: Bug
> Components: engine
> Affects Versions: 2.3.26-incubating
> Reporter: Ondra Žižka
> Fix For: 2.3.27-incubating
>
>
> The objects I feed to FreeMarker often cotain {{Iterator}}s rather than
> {{Collection}}s.
> While it's quite easy to write a FreeMarker function
> {{iteratorToList(Iterator)}}, it would be convenient to have the following:
> A built-in that would convert various models to a sequence. Could be named
> {{?seq}} or {{?sequence}}.
> Usage:
> {code}<#assign foo = myIterable?seq>{code}
> {code}<#assign foo = myIterator?seq>{code}
> * A sequence would stay intact.
> * An {{Iterable}} wrapped in FM model would become internally a {{List}} -
> all elements consumed and stored.
> For me, other cases are not that important, but with some imagination, other
> models could also leverage it, like,
> * A {{Stream}} could be also turned into a {{List}}.
> * A hash could turn into a sequence of key/value pairs. That could be useful
> for debugging purposes.
> I am not sure if I didn't propose that already, but I could only find
> FREEMARKER-62.
> Thanks for considering.
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