让子对象引用其父对象而不是指针是不好的做法吗？

Question

Related to this , I would like to know if there are reasons to use pointers to a parent object (not talking about a parent class) instead of references.

Obviously, if the parent could be null, a reference will not work. But what if the parent object creates and destroys the child object in its lifetime so that the child object's pointer back to its parent will never be null? I think it sounds okay in this case, but I have not seen others do it and am still learning a lot about C++.

The specific case I am thinking of is a specialized dialog window that will only be created by a certain window class.

What are some problems (if any) with doing

class Child {
    Child(Parent& parent) : parent_(parent) {}
    Parent& parent_;
};

versus

class Child {
    Child(Parent* parent) : parent_(parent) {}
    Parent* parent_;
};

Answer 1

People will argue about it all day long but references are just limited pointers. Don't agonize about which to use.

The advantage of a pointer is you can copy childs, or create a child without a parent, to be given one later. If you need to do this, you have to use a pointer.

If not, use whichever makes you feel warmest inside. It just isn't worth worrying about.

If you make the pointer Parent *const parent_ it is effectively the same as a reference.

Answer 2

here are some differences between references and pointers :

References :

• A reference must be initialized at creation time
• Once initialized to point to an object, you cant change the reference to point to another object

Pointers :

• A pointer does not need to be initialized, you can point to NULL
• You can modify your pointer in order to point to another object

Consequences :

Thus depending on the relationship you want to have between child and parents, you will choose pointer or reference. Also prefer reference to pointer if you dont need pointer.

In other words, if child object have the same parent during its lifetime and parent exists at the creation of the child : use reference to point to parent.