xslt - 在 xslt 的 for-each 循环中使用 position() 选择特定节点未返回预期结果

Question

我意识到这段代码不是最干净的，但不幸的是，正确地重构它不是一种选择。

问题是我希望 position() 在第二次迭代时返回一个真值。但是当使用 position() 时，它永远不会像第二次迭代那样返回 true。

但如果我对选择值进行硬编码，它会返回预期的结果。这是一个例子:

<root>
  <MainProducts>
    <MainProduct>
      <Published>0</Published>
    </MainProduct>
    <MainProduct>
      <Published>1</Published>
    </MainProduct>
  </MainProducts>
  <SubProducts>
    <SubProduct>
      <IsDefault>1</IsDefault>
    </SubProduct>
    <SubProduct>
      <IsDefault>0</IsDefault>
    </SubProduct>
  </SubProducts>
</root>

XML 内容:

<xsl:for-each select="/root/SubProducts/SubProduct">
  <script type="text/javascript">
    // Always returns false
    console.log("Dynamic position " + <xsl:value-of select="position()" /> + " IsDefault: " + ( <xsl:value-of select="/root/MainProducts/MainProduct[position()]/Published" /> == 1 ? "true" : "false" ));
  </script>
</xsl:for-each>

<script type="text/javascript">
  // Returns false, but expected to return true on second iteration.
  console.log("Hard coded position 1 IsDefault: " + ( <xsl:value-of select="/root/MainProducts/MainProduct[1]/Published" /> == 1 ? "true" : "false" ));

  // Returns true
  console.log("Hard coded position 2 IsDefault: " + ( <xsl:value-of select="/root/MainProducts/MainProduct[2]/Published" /> == 1 ? "true" : "false" ));
</script>

这是确切的控制台输出:

Dynamic position 1 IsDefault: false
Dynamic position 2 IsDefault: false
Hard coded position 1 IsDefault: false
Hard coded position 2 IsDefault: true

position() 没有正确选择节点，我在这里遗漏了什么？

Answer 1

  <script type="text/javascript">
    // Always returns false
    console.log("Dynamic position " + 
   <xsl:value-of select="position()" /> + 
    " IsDefault: " + 
      ( <xsl:value-of select="/root/MainProducts/MainProduct[position()]/Published" /> 
        == 1 ? "true" : "false" ));
  </script>

在上面的代码中 MainProduct[position()] 等同于 MainProduct[true()] )不要忘记 position() 是上下文相关的!

所以，您实际上是在评估:

<xsl:value-of select="/root/MainProducts/MainProduct/Published" />

并且这始终输出由 XPath 表达式选择的第一个 Published 元素的字符串值 -- 它恰好是 0。

正确的代码:

<xsl:variable name="vPos" select="position()"/>

  <script type="text/javascript">
    // Always returns false
    console.log("Dynamic position " + 
   <xsl:value-of select="position()" /> + 
    " IsDefault: " + 
      ( <xsl:value-of select=
             "/root/MainProducts/MainProduct[position()=$vPos]/Published" /> 
        == 1 ? "true" : "false" ));
  </script>

这是一个完整的转换:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="/">
   <xsl:for-each select="/*/SubProducts/SubProduct">
    <xsl:variable name="vPos" select="position()"/>

      <script type="text/javascript">
        console.log("Dynamic position " +
       <xsl:value-of select="position()" /> +
        " IsDefault: " +
          ( <xsl:value-of select=
             "/*/MainProducts/MainProduct
                         [position()=$vPos]/Published" />
            == 1 ? "true" : "false" ));
      </script>
  </xsl:for-each>
 </xsl:template>
</xsl:stylesheet>

当此转换应用于提供的 XML 文档时:

<root>
    <MainProducts>
        <MainProduct>
            <Published>0</Published>
        </MainProduct>
        <MainProduct>
            <Published>1</Published>
        </MainProduct>
    </MainProducts>
    <SubProducts>
        <SubProduct>
            <IsDefault>1</IsDefault>
        </SubProduct>
        <SubProduct>
            <IsDefault>0</IsDefault>
        </SubProduct>
    </SubProducts>
</root>

产生了想要的、正确的结果:

<script type="text/javascript">
        console.log("Dynamic position " +
       1 +
        " IsDefault: " +
          ( 0
            == 1 ? "true" : "false" ));
      </script>
<script type="text/javascript">
        console.log("Dynamic position " +
       2 +
        " IsDefault: " +
          ( 1
            == 1 ? "true" : "false" ));
      </script>