Question

I have a class

class PCB {
     public: 
     struct {
         string type;
         **linklist list;**//refer to list which contains PCB instance
     } status;
}

what i want is to create the class PCB instance, but the instance is in a linklist list. i build the linklist class as below

class linklist
{

   public:

     void append( PCB num );
};
void linklist::append(PCB num){
}

Error occus saying num above is in error type. what shall i do in this case?

Answer 1

1. You can use forward declaration:

   class linklist; // forward declaration
   
   class PCB {
   
     public:
        struct {
           string type;
           linklist list;  //refer to list which contains PCB instance
       } status;
   }
   

2. Or when you only refer to a type by reference or by pointer, you do not need to include it’s header file.

   linklist* list