Thread: Problem declaring instance of enclosing class within a nested struct

Basically have something like this:

Code:

struct enclosing
{
   struct nested
   {
      enclosing instance;      
   };   
};

For some reason the compiler complains that field 'instance' has incomplete type of {anonymous}::enclosing. I really don't want to have to make a forward declaration, pulling the struct outside of the class. Is there a nicer workaround for that?

Why do you want the nested struct to have an instance of the enclosing struct type in the first place? It is far more typical to expect that the enclosing struct would be the one to have an instance of the nested struct, or the nested struct might refer to the enclosing struct through a (smart) pointer. A forward declaration wouldn't cut it either since you need the struct definition, not a mere forward declaration, to declare an instance of it. Perhaps you would like to move the nested struct into a namespace instead?

Okay on second thought this might work after all. I put together a simplified version of what I'm trying to do and it compiled fine.

Code:

struct enclosing 
{     
    struct A 
    { 
        A(int val) 
        : var(val) 
        { 
            // blah blah blah 
        } 
         
        void operator()(enclosing& ref) 
        { 
            // do stuff here with "ref" using "var" 
        } 
         
        int var;         
    }; 
     
    template <typename E> 
    struct B 
    { 
        B(const E& val) 
        : dup(val) 
        { 
            // blah blah blah 
        } 
         
        void operator()(E& ref) 
        { 
            // do stuff here with "ref" using fields of "dup" 
        } 
         
        E dup;            
    };    
     
    template <typename G> 
    void work(G fun) 
    { 
        // do some things 
        fun(*this); 
        // do more stuff here 
    } 
     
    void work(int val) 
    { 
        work(A(val)); 
    } 
     
    void work() 
    { 
        work(B<enclosing>(*this)); 
    }     
}; 
 
int main() 
{ 
    enclosing e; 
    e.work(123); 
    e.work(); 
}

Now I just have to try to fix all the errors in my project to see if it will actually work in the wild.