How to implement child-parent aggregation link in C++?
- by Giorgio
Suppose that I have
three classes P, C1, C2,
composition (strong aggregation) relations between P <>- C1 and P <>- C2, i.e. every instance of P contains an instance of C1 and an instance of C2, which are destroyed when the parent P instance is destroyed.
an association relation between instances of C1 and C2 (not necessarily between children of the same P).
To implement this, in C++ I normally
define three classes P, C1, C2,
define two member variables of P of type boost::shared_ptr<C1>, boost::shared_ptr<C2>, and initialize them with newly created objects in P's constructor,
implement the relation between C1 and C2 using a boost::weak_ptr<C2> member variable in C1 and a boost::weak_ptr<C1> member variable in C2 that can be set later via appropriate methods, when the relation is established.
Now, I also would like to have a link from each C1 and C2 object to its P parent object. What is a good way to implement this?
My current idea is to use a simple constant raw pointer (P * const) that is set from the constructor of P (which, in turn, calls the constructors of C1 and C2), i.e. something like:
class C1
{
public:
C1(P * const p, ...)
: paren(p)
{
...
}
private:
P * const parent;
...
};
class P
{
public:
P(...)
: childC1(new C1(this, ...))
...
{
...
}
private:
boost::shared_ptr<C1> childC1;
...
};
Honestly I see no risk in using a private constant raw pointer in this way but I know that raw pointers are often frowned upon in C++ so I was wondering if there is an alternative solution.
