转换为枚举类型需要显式强制转换（static_cast，C样式强制转换或函数样式强制转换）枚举

Question

I have copied the variable data from enum type which is declared outside the structure to the enum type variable which is written inside structure but it is throwing building error as Conversion to enumeration type requires an explicit cast (static_cast, C-style cast or function-style cast)

enum TGenObjType                        //sundar
{
   TYPE_UNDEFINED 
   , TYPE_CAR      
    , TYPE_TRUCK     
    , TYPE_MOTORBIKE 
   , TYPE_BIKE      
  , TYPE_PEDESTRIAN
  };

struct SGenObjData
{
  enum TGenObjType                recogType                          ; /* #RTAS: input               */ /* Object type (vehicle, pedestrian, ...)                                      */
  enum TGenObjType                commuType                          ; /* #RTAS: input               */ /* Object type (vehicle, pedestrian, ...)                                      */
}; 


 ushort j(0);
   for (ulong i = 0; i < gol.mData.size(); ++i)
 {
   if (gol.mData[i].isValid > 0)
    {
     if (gol.mData[i].id <= OBJ_MAX_ID)
     {
        objectList.objectIdx[size_t(gol.mData[i].id)][size_t(SRC_LIST1)]           = ushort(j);

             switch (gol.mData[i].recognized_shape)
            {
            case EO_SHAPE_CAR       : objectList.objects[j].recogType =    TYPE_CAR           ; break;
            case EO_SHAPE_TRUCK     : objectList.objects[j].recogType = TYPE_TRUCK         ; break;
            case EO_SHAPE_MOTORBIKE : objectList.objects[j].recogType = TYPE_MOTORBIKE ; break;
           case EO_SHAPE_BIKE      : objectList.objects[j].recogType = TYPE_BIKE      ; break;
           case EO_SHAPE_PEDESTRIAN: objectList.objects[j].recogType = TYPE_PEDESTRIAN; break;
            case EO_SHAPE_UNDEFINED :                                                                  
            default                 :    myDataLst.objectList.objects[j].recogType =    TYPE_UNDEFINED ;
         }// throwing an error Conversion to enumeration type requires an explicit cast (static_cast, C-style cast or function-style cast)

can anyone tell me what went wrong?

Answer 1

A named enum is a distinct type. it has an underlying type and a "weak" enum allows implicit conversion to the underlying type. It does not support implicit conversion from the underlying type to the enum . An enum declared with the same name as another enum but in a different scopr is a distinct type of its own (this applies to all types). Since the enum does not support implicitly conversion from the underlying type you cannot simply assign the value of one enum to another, even if the enum 's and all of their members have identical names and values.

enum Foo
{
    Bar = 0
};

is not the same as

struct Object
{
    enum Foo
    {
        Bar = 0
    };
};

Both Foo and Object::Foo are distinct types and C++ does not allow implicitly conversion between them.

Object:Foo innerFoo = Bar; // Error Bar and Object::Bar are not the same

Object:Foo innerFoo = Onject::Bar; // OK! They are the same!

It sounds like the two enum 's are redundant so you need to decide which version of TGenObjType you want to use and delete the other.