[FREEMARKER-75] New built-in ?as("variableName") to store the left-hand operand to a variable.

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 2.3.26-incubating
• Component/s: engine
• Assignee: Unassigned
• Reporter: Ondra Žižka
• Created: 28/Sep/17 22:41
• Updated: 30/Sep/17 11:07
• Resolved: 30/Sep/17 11:07

Description

When coding templates, one often runs into a situation like this:

<#if (foo.bar.baz.expensiveCall())!false >
     ${ foo.bar.baz.expensiveCall() }
</#if>

Solving it with currently available things is something like

<#assign cached = (foo.bar.baz.expensiveCall())! >
<#if cached?has_content() >
     Hello, ${ cached }
</#if>

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.

<#if (foo.bar.baz.expensiveCall())!?as("cached")?has_content >
     Hello, ${ cached }
</#if>

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.)

${ "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

The new ?as() built-in could be also used for a more convenient way of assigning wile printing:

${"Hi ${user}"?as("greet")}.
${ greet }, again.

I hope my explanation does make sense.
Thanks for considering.

Issue Links

• relates to: FREEMARKER-76 New built-in ?if(condition, otherwise) to override left-hand expr. conditionally