使用 Boost property_tree 更新 XML 文件

发布于 2024-09-10 10:53:23 字数 696 浏览 5 评论 0原文

我有以下 XML 文件：

<xml version="1.0" encoding="utf-8"?>
<Data>
    <Parameter1>1</Parameter1>
</Data>

我想添加一个新节点： Parameter2="2" 到数据节点。这段代码不起作用，保存的文件仍然只包含一个参数：

    boost::property_tree::ptree tree;
    boost::property_tree::ptree dataTree;

    read_xml("test.xml", tree);
    dataTree = tree.get_child("Data");
    dataTree.put("Parameter2", "2");

    boost::property_tree::xml_writer_settings w(' ', 4);
    write_xml("test.xml", tree, std::locale(), w);

如果我在 dataTree.put 之后添加这两行，我会得到正确的结果：

    tree.clear();
    tree.add_child("Data", dataTree);

我不喜欢这个解决方案，因为它会产生更复杂的树结构问题。是否可以在不删除/添加子节点的情况下更新属性树？

原文

I have the following XML file:

<xml version="1.0" encoding="utf-8"?>
<Data>
    <Parameter1>1</Parameter1>
</Data>

I want to add a new node: Parameter2="2" to the Data node. This code doesn't work, saved file still contains only one parameter:

    boost::property_tree::ptree tree;
    boost::property_tree::ptree dataTree;

    read_xml("test.xml", tree);
    dataTree = tree.get_child("Data");
    dataTree.put("Parameter2", "2");

    boost::property_tree::xml_writer_settings w(' ', 4);
    write_xml("test.xml", tree, std::locale(), w);

If I add these two lines after dataTree.put, I get correct result:

    tree.clear();
    tree.add_child("Data", dataTree);

I don't like this solution, because it creates problems with more complicated tree structutes. Is it possible to update property tree without deleting/adding child nodes?

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柠檬色的秋千 2024-09-17 10:53:23

您的代码几乎是正确的，这是更新子节点的正确方法。

然而，有一个小错误。当您键入时：

dataTree = tree.get_child("Data");

您将“子”的副本分配给dataTree。因此，下一行指的是副本而不是您的层次结构。你应该写：

boost::property_tree::ptree &dataTree = tree.get_child("Data");

这样你就获得了对孩子的引用。

完整的例子是：

  using namespace boost::property_tree;
  ptree tree;

  read_xml("data.xml", tree);
  ptree &dataTree = tree.get_child("Data");
  dataTree.put("Parameter2", "2");

  xml_writer_settings<char> w(' ', 4);
  write_xml("test.xml", tree, std::locale(), w);

Your code is almost right, that is the right way to update a child node.

However, there is a small bug. When you type:

dataTree = tree.get_child("Data");

You assign to dataTree a copy of the "child". So, the next line refers to the copy and not to your hierarchy. You should write:

boost::property_tree::ptree &dataTree = tree.get_child("Data");

So you obtain a reference to the child.

The complete example is:

  using namespace boost::property_tree;
  ptree tree;

  read_xml("data.xml", tree);
  ptree &dataTree = tree.get_child("Data");
  dataTree.put("Parameter2", "2");

  xml_writer_settings<char> w(' ', 4);
  write_xml("test.xml", tree, std::locale(), w);

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