freemark（built-in）笔记一

原创于 2005-01-24 14:43:00 发布 · 1.1k 阅读

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博客提及exists、has_content、if_exists，还给出示例，假设不存在名为mouse的变量，说明了相关输出情况。

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default
如果存在就用本生的值，不存在就用缺省值

<#assign seq = ['a', 'b']>
${seq[0]?default('-')}
${seq[1]?default('-')}
${seq[2]?default('-')}
${seq[3]?default('-')} 
结果
 a
b
-
- 

 exists
 It is true if the variable exists, otherwise it is false. 

 has_content
 It is true if the variable exists and is not ``empty'', otherwise it is false. The meaning of ``empty'' depends on the concrete case. 
 expr?if_exists?size > 0 or expr?if_exists?length > 0 instead of expr?has_content. 

 if_exists
 Example. Assume no variable called mouse is present:
(${mouse?if_exists})
Creating mouse...
<#assign mouse = "Jerry">
(${mouse?if_exists})  
The output will be:
()
Creating mouse...
(Jerry)