C ++：解析XML文件（MXML库）时遇到麻烦

Question

我的以下代码有问题。

它使用Mini-XML库从xml文件中提取元素。

它编译并运行良好，除了它无法获取最后一个“半径元素”，而是返回NULL（如果我不检查子节点是否不为NULL，它将崩溃。）

//Start loading <ssys> elements
mxml_node_t *node; //temporary node to save
mxml_node_t *subnode; //temporary subnode to save
mxml_node_t *subnode2; //another temporary subnode to save
const char* name_tmp; //Temporary string for names of ssys
//Load first ssys
node = mxmlFindElement(Systems_elem, tree, "ssys", NULL, NULL, MXML_DESCEND);
cout << "Node 1 pointer: " << node<<endl<<endl;
//Start loading the rest of the ssys elements (but fail if first element is NULL)
int i = 1;
do {
    //Load node into vector of pointers
    ssys_elem.push_back(node);
    //Get name attribute
    name_tmp = mxmlElementGetAttr(node, "name");
    ssys_name.push_back(name_tmp);
    //load next ssys
    node = mxmlFindElement(node, tree, "ssys", NULL, NULL, MXML_NO_DESCEND);
    cout << "Node: " << node<<endl<<endl;
    cout<<"Name: " <<name_tmp<<endl<<endl;
    //Descend to radius element
    subnode = mxmlFindElement(node, tree, "radius", NULL, NULL, MXML_DESCEND);
    //
    if(subnode != NULL){
        cout <<subnode->child->value.text.string<<endl<<endl; <--Trouble Here
    }
   i++;
}
while (node != NULL);

}

这是一个有问题的XML文件：

 <ssys name="Zylex">
  <general>
   <radius>3500.000000</radius> <-- I am trying to get "3500.000000"
   <stars>400</stars>
   <asteroids>0</asteroids>
   <interference>300.000000</interference>
   <nebula volatility="0.000000">250.000000</nebula>
  </general>
  <pos>
   <x>438.000000</x>
   <y>-34.000000</y>
  </pos>
  <assets/>
  <jumps>
   <jump target="Arcanis">
    <pos x="-3418.937501" y="-748.910119"/>
    <radius>200.000000</radius>
    <flags>
     <autopos/>
    </flags>
   </jump>
   <jump target="Doeston">
    <pos x="2991.156265" y="1817.411401"/>
    <radius>200.000000</radius>
    <flags>
     <autopos/>
    </flags>
   </jump>
  </jumps>
 </ssys>
</Systems>

此代码有什么问题？

Answer 1

好吧，我猜您在谈论的是Mini-XML，我实在没有经验。 我看到的是，您的迭代器比您的名字领先了一步。 我认为您想要更多类似的东西：

node = mxmlFindElement(Systems_elem, tree, "ssys", NULL, NULL, MXML_DESCEND);
while (node) {
    ssys_elem.push_back(node);
    name_tmp = mxmlElementGetAttr(node, "name");
    ssys_name.push_back(name_tmp);

    cout << "Node: " << node << endl << endl;
    if (name_tmp) {
        cout << "Name: " << name_tmp << endl << endl;
    }

    // Descend to radius element
    subnode = mxmlFindElement(node, tree, "radius", NULL, NULL, MXML_DESCEND);
    if (subnode != NULL){
        cout << subnode->child->value.text.string << endl << endl; <--Trouble Here
    }

    // iterate at the end!
    node = mxmlFindElement(node, tree, "ssys", NULL, NULL, MXML_NO_DESCEND);
}

通常，永远不要相信您拥有格式正确的XML。 即使您认为应该有孩子，也要始终检查NULL。 希望能有所帮助。