When to use pointers in a class?

[Joe Van Dyk]

Is there some rule of thumb about when to use pointers to an object and
when to use a reference* to an object when a class needs to have objects
as data members?

Example:
class A
{
B* b_ptr;
B b;
vector<B*> vector_ptrs;
vector<B> vector_objects;
};

How do I know when to use pointers and when not to use them?

Thanks,
Joe

* I'm not sure if my terminology is correct here, please correct me if
I'm wrong. I'm also slightly confused about the relationship between
references and pointers. I know a reference is an alias of an object
and a pointer contains some address that's usually the start of the
object's location in memory, but I'm still not sure what the real
difference is.

[I V]

Joe Van Dyk wrote:

class Image
{
public:
typedef unsigned int color_type;
Image(size_t width, size_t height);
It looks like Magick++ uses unsigned int, rather than size_t for height
and width specifications. Maybe your application ought to use the same?

[...]
Do I want to use references to the member objects here? Or pointers?
I'm having difficulties initializing the objects if they are references
and aren't passed in to the Image constructor.

Do you need to store the Geometry and ColorRGB objects at all? If
they're only being used as arguments to the Magick::Image constructor,
they can probably be local variables in your Image constructor.
Otherwise, you probably want to store the actual objects in your class
- neither reference nor pointer.

If the Magick::Image object has the same lifetime as your Image class,
then you probably want to store it directly in your class (again,
neither pointer nor reference). If the Magick::Image object is created
at some point after your Image object, or will be destroyed sometime
before your Image object, you should use a pointer.