Why can't I do this?
class A
{
public:
int a, b;
};
class B : public A
{
B() : A(), a(0), b(0)
{
}
};
ベストアンサー1
You can't initialize a
and b
in B
because they are not members of B
. They are members of A
, therefore only A
can initialize them. You can make them public, then do assignment in B
, but that is not a recommended option since it would destroy encapsulation. Instead, create a constructor in A
to allow B
(or any subclass of A
) to initialize them:
class A
{
protected:
A(int a, int b) : a(a), b(b) {} // Accessible to derived classes
// Change "protected" to "public" to allow others to instantiate A.
private:
int a, b; // Keep these variables private in A
};
class B : public A
{
public:
B() : A(0, 0) // Calls A's constructor, initializing a and b in A to 0.
{
}
};