[jira] [Comment Edited] (FREEMARKER-37) ability to skip iteration in a list

["Ondra Žižka (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FREEMARKER-37?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16187662#comment-16187662 ] 

Ondra Žižka edited comment on FREEMARKER-37 at 10/2/17 5:09 AM:
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I agree that just having {{<#continue>}} might lead to an unexpected/undefined behavior with things like counters, separators etc.

How about having {{<#continue>}} and {{<#skip>}} ?   {{<#continue>}} would count as item used, {{<#skip>}} would not. This would pass the responsibility to decide whether to increment the counter or not to the user. It makes sense, because the user knows whether he uses {{is_even_item}} for coloring table rows, and whether that was already taken care of (then they would use {{<#continue>}}) or not (then he would use {{<#skip>}}).

I.e.

{code}
<#list 10..15 as num>
    <#if num == 10> 
        <#continue>
    </#if>
    <#if num == 11> 
        <#skip>
    </#if>
    [${num.index}] ==  ${num}, ${num.count} items passed, is_first = ${num.is_first?c}
</#list>
{code}

This would print 
2 == 12, 1 items passed, is_first=false  (I hope I computed right :)
...
Because the {{.counter}} would increment only if the loop is finished or continued, {{is_first}} would derive from the {{counter == 0}}. 

Similarly, {{is_even_item}} and {{is_odd_item}} would check the counter rather than index.

{{is_last}} would probably have to rely on {{index}}.

Similarly, separators could appear if {{couter > 0 and index < size-1}}, and, well, the user would have to have some common sense not to expect the separator appear if he uses {{<#skip>}} before {{<#sep>}}. 


was (Author: pekarna):
I agree that just having {{<#continue>}} might lead to an unexpected/undefined behavior with things like counters, separators etc.

How about having {{<#continue>}} and {{<#skip>}} ?   {{<#continue>}} would count as item used, {{<#skip>}} would not. I.e.

{code}
<#list 10..15 as num>
    <#if num == 10> 
        <#continue>
    </#if>
    <#if num == 11> 
        <#skip>
    </#if>
    [${num.index}] ==  ${num}, ${num.count} items passed, is_first = ${num.is_first?c}
</#list>
{code}

This would print 
2 == 12, 1 items passed, is_first=false
...
Because the {{.counter}} would increment only if the loop is finished or continued, {{is_first}} would derive from the {{counter == 0}}. Similarly, {{is_even_item}} and {{is_odd_item}} would check the counter rather than index. {{is_last}} would probably have to rely on {{index}}. Similarly, separators could appear if {{couter > 0 and index < size-1}}, and, well, the user would have to have some common sense not to expect the separator appear if he uses {{<#skip>}} before {{<#sep>}}. 

> ability to skip iteration in a list
> -----------------------------------
>
>                 Key: FREEMARKER-37
>                 URL: https://issues.apache.org/jira/browse/FREEMARKER-37
>             Project: Apache Freemarker
>          Issue Type: Improvement
>            Reporter: Ivan Levchenko
>
> Sorely missing ability to skip through an iteration of a list and continue on with the rest of the list. would like to write clean code like this:
> <#list collection as element>
>         <#if element.attr1 == "some_value"> 
>                 <#continue />  <#-- skip over this item and run next item in loop -->
>         </#if>
>     do stuff here
> </#list>
> Thanks!



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