查找XML与升压关键 [英] Find Key in XML with Boost

问题描述

我使用的是旧code基地内首次提升，我们有

  iptree孩子= pt.get_child（字段名）;
对于（const的汽车和放大器; KV：儿童）{
    提高:: property_tree :: iptree子树=（的boost :: property_tree :: iptree）kv.second;
//递归调用
}
 

我的问题是有时字段名不`吨存在XML文件中，我有一个例外

我试过：

 的boost :: property_tree :: iptree :: assoc_iterator吧= pt.find（字段名）;
 

但我不知道如何使用它，我不能老是用的：if（！它= NULL）

任何帮助，请将AP preciated

我使用VS 2012

如果它`很复杂的是还有没有其他的方式来阅读嵌套节点的XML？我的工作是，已有3天

这是XML的例子

 ＆LT;？XML版本=1.0编码=UTF-8＆GT？;
＆LT; nodeA上的xmlns：XSI =htt​​p://www.w3.org/2001/XMLSchema-instance的xmlns：XSD =htt​​p://www.w3.org/2001/XMLSchema＆GT;
  ＆所述; nodeA.1＆gt;这是住址＆下; /nodeA.1>
    ＆LT; nodeA.2＆GT;
    ＆LT;＆节点1 GT;
      ＆LT; node1.1＆GT;
        ＆LT; node1.1.1＆GT;女＆LT; /node1.1.1>
        ＆所述; node1.1.2＆GT; 23℃; /node1.1.2>
        ＆LT; node1.1.3＆GT;＆工程师LT; /node1.1.3>
      ＆LT; /node1.1>
      ＆LT; node1.2＆GT;
        ＆LT; node1.2.1＆GT;女＆LT; /node1.2.1>
        ＆所述; node1.2.2＆GT; 35℃/node1.2.2>
        ＆LT; node1.2.3＆GT;医生和LT; /node1.2.3>
      ＆LT; /node1.2>
    ＆LT; /节点1＆GT;
＆LT; /nodeA.2>
＆LT; nodeA.3＆GT;汽车1 LT; /nodeA.3>
＆LT; / nodeA上＆GT;
 

解决方案

使用pt.get_child_optional（...），以prevent异常。 pt.find（...）返回其失败比较真实的pt.not_found（）的迭代器。

编辑：如何使用boost ::可选＆LT; --->

 的boost ::可选＆LT; iptree＆安培; ＆GT; CHL = pt.get_child_optional（字段名）;    如果（CHL）{
      为（自动答：* CHL）
        的std :: CERR＆LT;＆LT; ：＆所述;＆下; a.first＆LT;＆LT; ：＆所述;＆下;的std :: ENDL;
    }
 

I am using boost for the first time within an old code base that we have

iptree children = pt.get_child(fieldName);
for (const auto& kv : children) { 
    boost::property_tree::iptree subtree = (boost::property_tree::iptree) kv.second ;
//Recursive call
}

My problem is sometimes the fieldName doesn`t exist in the XML file and I have an exception

I tried :

boost::property_tree::iptree::assoc_iterator it = pt.find(fieldName);

but I dont know how to use the it I can`t use: if (it != null)

Any help please will be appreciated

I am using VS 2012

If it`s very complicated is there any other way to read a XML with nested nodes? I am working on that since 3 days

This is an Example of the XML

<?xml version="1.0" encoding="utf-8"?>
<nodeA xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <nodeA.1>This is the Adresse</nodeA.1>
    <nodeA.2>
    <node1>
      <node1.1>
        <node1.1.1>Female</node1.1.1>
        <node1.1.2>23</node1.1.2>
        <node1.1.3>Engineer</node1.1.3>
      </node1.1>
      <node1.2>
        <node1.2.1>Female</node1.2.1>
        <node1.2.2>35</node1.2.2>
        <node1.2.3>Doctors</node1.2.3>
      </node1.2>
    </node1>
</nodeA.2>
<nodeA.3>Car 1</nodeA.3>
</nodeA>

解决方案

Use pt.get_child_optional(...) to prevent an exception. pt.find(...) returns an iterator which compares true to pt.not_found() on failure.

EDIT: How to use boost::optional<--->

boost::optional< iptree & > chl =  pt.get_child_optional(fieldname); 

    if(chl) { 
      for( auto a : *chl ) 
        std::cerr << ":" << a.first << ":" << std::endl; 
    } 

这篇关于查找XML与升压关键的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！