one #macro add a field and a case (in switch-case)

问题

How to define macro (ALL_SWITCH) to recognize another macro (SINGLE_CASE) occurrences as list, and insert codes into 2 different places?

Is it possible?

Example

I want to create macro that have syntax roughly similar as :-

 SINGLE_CASE <Class Name> <Enum slot>  //add fields
 ALL_SWITCH              //recognize all calling SINGLE_CASE (see below)

Below is the expected usage.

TopHeader.h:-

 SINGLE_CASE Machine slot1
 SINGLE_CASE Machine slot2
 //^-------- will be replaced by below code (generate the whole class)
 template<class T> Sloter<Machine> : public GameObject {
     public: int slot1;  
     public: int slot2;          
 };

 SINGLE_CASE Turret slot3
 //^-------- will be replaced by below code 
 template<class T> Sloter<Turret>  : public GameObject {
     public: int slot3;            
 };

Manager.h:-

 class Manager{
     enum SlotX{ slot1,slot2,slot3 };
     public: int* provider(GameObject* gameObject, SlotX slotX){
         switch(slotX){
             ALL_SWITCH 
             //^---- will be replaced by below code (add only cases)
             case slot1:{ 
                 return &(static_cast<Machine*>(gameObject)->slot1); 
             }break;
             case slot2:{ 
                 return &(static_cast<Machine*>(gameObject)->slot2); 
             }break;
             case slot3:{ 
                 return &(static_cast< Turret*>(gameObject)->slot3); 
             }break;
         }
     }
 };

It is not a good design, but it is a simple example to consider whether MACRO can do something aggregate.

This feature is useful when I really want ultimate performance and flexibility,
e.g. store index into member itself for extremely-fast hashMap.

I have read :-

Creating a string list and an enum list from a C++ macro
It is too simple.
How can I generate a list via the C preprocessor (cpp)?
SINGLE_CASE (FUNCTION_TABLE in the solution) contains code, while mine does not.

I am not sure whether x-macros tag is appropriate.
(I have limited knowledge in this area.)

My progress

#define SINGLE_CASE( ClassName, slotX) /
template<class T> Sloter<ClassName> : public GameObject { /
     public: int slotX;  /
};

I still don't know how to make it support many slot for the same class or code ALL_SWITCH.
I am considering defining some kinds of table in macro, then make other macro read it. (not possible?)

来源：https://stackoverflow.com/questions/42383375/one-macro-add-a-field-and-a-case-in-switch-case

标签

c++

c++11

macros

x-macros