'.' : left operand points to 'class-key', use '–>'
The left operand of the member selection operator (.) was a pointer to a class, structure, or union.
The left operand of the member selection operator must be a class, structure, or union.
The following is an example of this example:
struct S
{
public:
int member;
} s, *ps;
void main()
{
ps.member = 0; // error, ps points to structure S
ps->member = 0; // OK, ps points to a structure S
s.member = 0; // OK, s is a structure type
}