Question

How to initialize an inner structure inside the outer structure?

struct TOuter
{
   struct TInner
   {
       bool b1, b2;
       TInner () : b1 (false), b2(false) {}
   };

   bool b3;

   TOuter (): TOuter::TInner(), b3(true) {} // Error
};

Answer 1

In this case, you have no object of the TInner struct, so there’s no need to initialize anything.

Other than that, it’s just the same as with any other class/struct type:

struct TOuter
{
   struct TInner
   {
       bool b1, b2;
       TInner () : b1 (false), b2(false) {}
   };

   bool b3;

   TInner foo;

   TOuter (): foo(), b3(true) { // member variable
     TInner x; // local variable
   }
};

TOuter::TInner out; // need qualified name, bc. TInner is not in scope
...
bar(TOuter::TInner()); // temporary