structure nesting problem

[chenci107]

I first defined a structure MotorData, and then used MotorData in the new structure RobotData, my structure is as follows：

typedef struct
{
  float pos;
  float vel;
  float tor;
  float temperature;
} MotorData;

struct RobotData
{
  union
  {
    MotorData joint_data[12];
    struct
    {
      MotorData fl_leg[3];
      MotorData fr_leg[3];
      MotorData hl_leg[3];
      MotorData hr_leg[3];
    };
  };
};

I tried the method in the tutorial,

struct Pet {
    enum Kind {
        Dog = 0,
        Cat
    };

    struct Attributes {
        float age = 0;
    };

    Pet(const std::string &name, Kind type) : name(name), type(type) { }

    std::string name;
    Kind type;
    Attributes attr;
};
py::class_<Pet> pet(m, "Pet");

pet.def(py::init<const std::string &, Pet::Kind>())
    .def_readwrite("name", &Pet::name)
    .def_readwrite("type", &Pet::type)
    .def_readwrite("attr", &Pet::attr);

py::enum_<Pet::Kind>(pet, "Kind")
    .value("Dog", Pet::Kind::Dog)
    .value("Cat", Pet::Kind::Cat)
    .export_values();

py::class_<Pet::Attributes>(pet, "Attributes")
    .def(py::init<>())
    .def_readwrite("age", &Pet::Attributes::age);

But since my structure MotorData is defined outside RobotData, I get an error "Class RobotData has no member MotorData"
how should I deal with this situation?