Thymeleaf:检查是否定义了变量 [英] Thymeleaf: check if a variable is defined

问题描述

如何检查 Thymeleaf 中是否定义了变量 ?

How can I check if a variable is defined in Thymeleaf?

在Javascript中是这样的:

Something like this in Javascript:

if (typeof variable !== 'undefined') { }

或者在PHP中这样:

if (isset($var)) { }

胸腺有等同体吗?

推荐答案

是的，您可以使用以下代码轻松检查文档的给定属性是否存在.请注意，如果满足条件，您将创建div标记:

Yes, you can easily check if given property exists for your document using following code. Note, that you're creating div tag if condition is met:

<div th:if="${variable != null}" th:text="Yes, variable exists!">
   I wonder, if variable exists...
</div>

如果您想使用variable的字段，则值得检查此字段是否也存在

If you want using variable's field it's worth checking if this field exists as well

<div th:if="${variable != null && variable.name != null}" th:text="${variable.name}">
   I wonder, if variable.name exists...
</div>

甚至更短，无需使用if语句

Or even shorter, without using if statement

<div th:text="${variable?.name}">
   I wonder, if variable.name exists...
</div>`

但是使用此语句，无论variable还是variable.name存在，您都将结束创建div标记

But using this statement you will end creating div tag whether variable or variable.name exist

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