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我有这个看起来像这样的 XML 树（我已经更改了标签名称，但如果你真的很聪明，你可能会弄清楚我实际上在做什么。）

<ListOfThings>
   <Thing foo:action="add">
      <Bar>doStuff --slowly</Bar>
      <Index>1</Index>
   </Thing>
   <Thing foo:action="add">
      <Bar>ping yourMother.net</Bar>
      <Index>2</Index>
   </Thing>
</ListOfThings>

使用 libxml2，我想以编程方式将新事物标记插入 ListOfThings，索引是当前最高索引，加一。我这样做（为简洁起见，删除了完整性检查）：

xpath = "//urn:myformat[@foo='bar']/"
        "urn:mysection[@name='baz']/"
        "urn:ListOfThings/urn:Thing/urn:Index";

xpathObj = xmlXPathEvalExpression(xpath, xpathCtx);
nodes = xpathObj->nodesetval;

/* Find last value and snarf the value of the tag */
highest = atoi(nodes->nodeTab[nodes->nodeNr - 1]->children->content);
snprintf(order, sizeof(order), "%d", highest + 1); /* highest index plus one */

/* now move up two levels.. */
cmdRoot = nodes->nodeTab[nodes->nodeNr - 1];
ASSERT(cmdRoot->parent && cmdRoot->parent->parent);
cmdRoot = cmdRoot->parent->parent;

/* build the child tag */
newTag = xmlNewNode(NULL, "Thing");
xmlSetProp(newTag, "foo:action", "add");

/* set new node values */
xmlNewTextChild(newTag, NULL, "Bar", command);
xmlNewChild(newTag, NULL, "Index", order);

/* append this to cmdRoot */
xmlAddChild(cmdRoot, newTag);

但是如果我调用这个函数两次（添加两个事物），XPath 表达式不会捕获我创建的新条目。有没有我需要调用的函数来踢 XPath 并让它确保它真的再次查看整个 xmlDocPtr？它显然确实被添加到了文档中，因为当我保存它时，我得到了我添加的新标签。

为了清楚起见，输出如下所示：

<ListOfThings>
   <Thing foo:action="add">
      <Bar>doStuff --slowly</Bar>
      <Index>1</Index>
   </Thing>
   <Thing foo:action="add">
      <Bar>ping yourMother.net</Bar>
      <Index>2</Index>
   </Thing>
   <Thing foo:action="add">
      <Bar>newCommand1</Bar>
      <Index>3</Index>
   </Thing>
   <Thing foo:action="add">
      <Bar>newCommand2</Bar>
      <Index>3</Index> <!-- this is WRONG! -->
   </Thing>
</ListOfThings>

I used a debugger to check what happened after xmlXPathEvalExpression got called and I saw that nodes->nodeNr was the same each time.

Help me, lazyweb, you're my only hope!

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1 回答 1

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Based on your XPath it looks like that is just a snippet of a namespaced document (using default namespace at that). I bet you made a prior call to register "urn" as the prefix for a namespace using xmlXPathRegisterNs. When you add the new nodes, you aren't creating them in namespaces so the XPath is correctly only picking the namespaced "Index" elements.

于 2010-03-18T14:22:38.203 回答