类数据成员struct：访问struct成员

Question

I have created a simple class called Foo, which contains a data member, Bar, which is a struct.

class Foo
{
  public :
  struct Bar {
    int a;
  };
};

I'd like to be able to access members in the struct either from functions I define in the class, or from the driver file, but I'm not sure how. Note: I've declared Bar as a public member because I am trying to access the members directly without using a get function. There is method in my madness, but I'll get to that later, so please accept that I want the struct to be public for now.

This is a very stripped down version of a larger program, so please forgive the simplicity.

Answer 1

I have created a simple class called Foo, which contains a data member, Bar, which is a struct.

Not really. Foo doesn't contain any data members at all. It just defines a type called Foo::Bar . An object of type Foo::Bar has an int data member named a , but a Foo object itself doesn't have any Bar or int subobjects.

If you do want an object of type Bar in every Foo , you need to declare that member with some name:

class Foo
{
  public :
  struct Bar {
    int a;
  };
  Bar bar;
};

This would let you do things like:

void test() {
    Foo f;
    f.bar.a = 5;
}