如何同时从嵌套映射中检索键字符串

Question

我有一个嵌套的 std::map 学生信息，如下所示：

{
 "class":[
         "student":{
             "name":"Collin",
             "average":"100",
             "family":{
             "%type":"nuclear",
             "%parent":"divorced",
             "#text":"3"
             } //family
          } //student
          "student":{
             "name":"Jamie",
             "average":"95",
             "family":{
             "%type":"nuclear",
             "%parent":"single",
             "#text":"2"
             } //family
          } //student
   ] //class
}//overall Map

where(above) - {} represents a Map
             - [] represents a List

我正在尝试检索这样的信息：

std::string student0Name = l_mapClassOfStudents[std::string("class")][std::string("student")][0][std::string("name")]; //see error message about operator for [ before student

但是，我没有找到与这些操作数匹配的运算符 []。这是在上面一行中学生之前的[右边。

我看到了这个 list inside map，但它没有说明如何取出物品。

编辑：这就是我最后的结果，使用我们对 String、VariantMap、VariantList、Variant 的内部定义（希望它们与标准 Variant、VariantMap、VariantList 紧密映射，但我不确定它是否确实如此或不是):

//Collin
VariantMap familyInfo0;
familyInfo0[String("%type")] = Variant("nuclear");
familyInfo0[String("%parent")] = Variant("single");
familyInfo0[String("#text")] = Variant("3");
VariantMap studentInfo0;
studentInfo0[String("name")] = Variant("Collin");
studentInfo0[String("average")] = Variant("100");
studentInfo0[String("family")] = familyInfo0;

VariantMap classInfo;
VariantList students;
VariantMap studentMap0;
studentMap0[String("student")] = studentInfo0;
VariantMap studentMap1;
studentMap1[String("student")] = studentInfo1;
students.push_back(studentMap0);
students.push_back(studentMap1);
classInfo[String("class")] = students;
Variant student0Name = classInfo[String("class")].cast<VariantList>()[0].cast<VariantMap>()[String("name")];

Answer 1

如果学生在列表中，使用 front() 检索第一个元素：

std::string student0Name = l_mapClassOfStudents[std::string("class")].front()[std::string("name")];

我认为更好的结构应该是

typedef map<string,string> Student;
typedef list<Student> Class;
typedef list<Class> School;

列表通常用于遍历。或者，您可以使用向量而不是列表来按编号访问它们：

typedef map<string,string> Student;
typedef vector<Student> Class;
typedef vector<Class> School;
cout << thisSchool[3][2]["name"]; // name of the 3rd student in the 4th class, if thisSchool is of type School (and enough classes and students exist)

如何同时从嵌套映射中检索键字符串

How to retrieve string of keys out of nested map at same time

c++

stdmap

stdlist