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https://issues.apache.org/jira/browse/FREEMARKER-75?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16187036#comment-16187036
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Daniel Dekany commented on FREEMARKER-75:
-----------------------------------------
{{#assign}}-like behavior is not a good default when used inside macros and
functions... you almost always want to set a local variable.
> New built-in ?as("variableName") to store the left-hand operand to a variable.
> ------------------------------------------------------------------------------
>
> Key: FREEMARKER-75
> URL: https://issues.apache.org/jira/browse/FREEMARKER-75
> Project: Apache Freemarker
> Issue Type: New Feature
> Components: engine
> Affects Versions: 2.3.26-incubating
> Reporter: Ondra Žižka
>
> When coding templates, one often runs into a situation like this:
> {code}
> <#if (foo.bar.baz.expensiveCall())!false >
> ${ foo.bar.baz.expensiveCall() }
> </#if>
> {code}
> Solving it with currently available things is something like
> {code}
> <#assign cached = (foo.bar.baz.expensiveCall())! >
> <#if cached?has_content() >
> Hello, ${ cached }
> </#if>
> {code}
> In short, passing around the information that a value could not be obtained
> is a bit cumbersome.
> What I suggest is a built-in that would capture a value of an expression on
> the left to a new variable and pass it along.
> {code}
> <#if (foo.bar.baz.expensiveCall())!?as("cached")?has_content >
> Hello, ${ cached }
> </#if>
> {code}
> The benefits is that there is need to compute the expression twice or do the
> assignment.
> Speaking of simplifying, the expression above could also be simplified by
> another built-in, a "reversed" {{then()}}. (For that I will file another
> jira.)
> {code}
> ${ "Hi, "?if( expensive()?as("cached"), "") + cached } // For conditional
> prefixes
> ${ expensive()?as("cached")!false + ", good bye!"?if(cached) } // For
> conditional suffixes
> ${ "Hi, ${expensive()?as("cached")!false}, again!"?if(cached) } // For
> conditional surrounding
> {code}
> The new {{?as()}} built-in could be also used for a more convenient way of
> assigning wile printing:
> {code}
> ${"Hi ${user}"?as("greet")}.
> ${ greet }, again.
> {code}
> I hope my explanation does make sense.
> Thanks for considering.
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