How to declare a structure variable IN THE MAIN FUNCTION in the case of structure within a structure? Why does this code generate error?

Question

Every time I try to write something like this, I get 2 errors saying-

• 'struct Outer' has no member named 'i2'

• 'struct Outer' has no member named 'i2'

  Both of these occur when using i2 in printf and scanf.

    struct Outer
    {
     int val1;
     struct Inner
     {
      int val2;
     };
    };

    int main()
    {
     struct Outer o1;
     struct Inner i2;

     printf("-----To access outer structure-----\n");
     printf("Input for val1\n");
     scanf("%d",&o1.val1);

     printf(----To access inner structure----\n);
     printf("Input for val2\n");
     scanf("%d",&o1.i2.val2); //generates error

     printf("Output for outer structure is %d\n",o1.val1);
     printf("Output for inner structure is %d\n",o1.i2.val2);//generates error
     return 0;
    }

Answer 1

The inner struct is only a definition of a struct. You need to declare a member of that type in the outer class.

struct Outer
{
    struct Inner
    {
        int val2;
    }; // We have defined a struct here

    int val1;
    struct Inner i2; // We have declared a member of that struct type here
};

Now you only define the outer class on your main function:

int main()
{
    struct Outer o1;

    ...

Note that there's no actual need to declare the Inner struct inside the declaration of the Outer struct. They can be totally separate.

Answer 2

Define the structs separately (there is no concept of embedded structs in C)

struct Inner { int val2; };
struct Outer { int val1; struct Inner x; };

Then use an object of the struct Outer type

int main(void) {
    struct Outer in1, in3;
    struct Inner in2;

    in1.val1 = -1;
    in1.x.val2 = -42;

    in2.val2 = 42;

    in3.x = in2;
}