xml 如何在 XSL 中为每个测试引用当前节点值？
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How to refer to current node value in XSL for-each test?
提问by Ben Blank
Let's say I have an XML doc like this:
假设我有一个这样的 XML 文档：
<books>
<book>1110</book>
<book>1111</book>
<book>1112</book>
<book>1113</book>
</books>
I'm trying to setup a condition that tests the value of the current node in the for-each, but I'm doing something wrong:
我正在尝试设置一个条件来测试 中当前节点的值for-each，但我做错了：
<xsl:for-each select="/books/book">
<xsl:if test=".[='1112']">
Success
</xsl:if>
</xsl:for-each>
What am I doing incorrectly?
我做错了什么？
回答by Ben Blank
Using .can, indeed, refer to the current (or "context") node, but not the way you're using it here. In XPath, .[foo]is not valid syntax — you need to use self::node()[foo]instead. Also, the =operator needs something to match against, in this case the text()selector to access the element's text contents:
.实际上，使用can 指的是当前（或“上下文”）节点，但不是您在此处使用它的方式。在 XPath 中，.[foo]是无效的语法 — 您需要self::node()[foo]改用。此外，=操作符需要匹配一些东西，在这种情况下，text()选择器访问元素的文本内容：
<xsl:for-each select="/books/book">
<xsl:if test="self::node()[text()='1112']">
Success
</xsl:if>
</xsl:for-each>
As stated in the other answers, however, unless your for-eachis performing other operations as well, you don't need to iterate at all and can use just ifto accomplish the same task:
但是，如其他答案中所述，除非您for-each还执行其他操作，否则您根本不需要迭代，只需使用if即可完成相同的任务：
<xsl:if test="/books/book[. = 1112]">
Success
</xsl:if>
回答by Dimitre Novatchev
I'm trying to setup a condition that tests the value of the current node in the for-each, but I'm doing something wrong:
我正在尝试设置一个条件来测试 for-each 中当前节点的值，但我做错了：
The first thing that is incorrect is the syntax:
首先不正确的是语法：
.[='1112']
There are two things wrong here:
这里有两件事不对：
Within [ and ] there is no predicate: the "=" operator needs two arguments but only one is provided.
.[x = y]is still invalid syntax, although the predicate is OK. This has to be specified as:self::node()[condition]
在 [ 和 ] 中没有谓词：“=”运算符需要两个参数，但只提供了一个参数。
.[x = y]虽然谓词是 OK ，但仍然是无效的语法。这必须指定为：self::node()[条件]
The second thingin the provided code that can be improvedis the <xsl:for-each>instruction, which isn't necessary at all; A single XPath expression will be sufficient.
提供的代码中可以改进的第二件事是<xsl:for-each>指令，这根本不是必需的；单个 XPath 表达式就足够了。
To summarize, one possible XPath expression that evaluates to the required boolean value is:
总而言之，计算为所需布尔值的一种可能的 XPath 表达式是：
/books/book[. = '1112']
If it is really necessary that the condition be tested inside the <xsl:for-each>instruction, then one correct XPath expression I would use is:
如果确实有必要在<xsl:for-each>指令中测试条件，那么我将使用的一种正确的 XPath 表达式是：
. = '1112'
The aboveis a string comparison and may not evaluate to true()if there are spaces around. Therefore, a numerical comparison may be better:
以上是字符串比较，如果周围有空格，可能无法评估true()。因此，数值比较可能更好：
. = 1112
回答by Dominic Cronin
XSLT has a function specially for this problem.
XSLT 有一个专门针对这个问题的功能。
回答by tcurdt
While Ben has answered your question correctly, using for-each is most definitely the wrong general approach. After all this is XSLT. So you are probably more looking for something like this:
虽然 Ben 正确回答了您的问题，但使用 for-each 绝对是错误的一般方法。毕竟这是XSLT。所以你可能更喜欢这样的东西：
<xsl:if test="/books/book[text()='1112']">
Success
</xsl:if>
回答by Shaiful Islam
Try with this
试试这个
<xsl:for-each select="/books/book">
<xsl:if test="current() = '1112'">
Success
</xsl:if>
</xsl:for-each>
