Are static fields inherited?
When static members are inherited, are they static for the entire hierarchy, or just that class, i.e.:
class SomeClass
{
public:
SomeClass(){total++;}
static int total;
};
class SomeDerivedClass: public SomeClass
{
public:
SomeDerivedClass(){total++;}
};
int main()
{
SomeClass A;
SomeClass B;
SomeDerivedClass C;
return 0;
}
would total be 3 in all three instances, or would it be 2 for SomeClass
and 1 for SomeDerivedClass
?
Solution 1:
The answer is actually four in all cases, since the construction of SomeDerivedClass
will cause the total to be incremented twice.
Here is a complete program (which I used to verify my answer):
#include <iostream>
#include <string>
using namespace std;
class SomeClass
{
public:
SomeClass() {total++;}
static int total;
void Print(string n) { cout << n << ".total = " << total << endl; }
};
int SomeClass::total = 0;
class SomeDerivedClass: public SomeClass
{
public:
SomeDerivedClass() {total++;}
};
int main(int argc, char ** argv)
{
SomeClass A;
SomeClass B;
SomeDerivedClass C;
A.Print("A");
B.Print("B");
C.Print("C");
return 0;
}
And the results:
A.total = 4
B.total = 4
C.total = 4
Solution 2:
3 in all cases, since the static int total
inherited by SomeDerivedClass
is exactly the one in SomeClass
, not a distinct variable.
Edit: actually 4 in all cases, as @ejames spotted and pointed out in his answer, which see.
Edit: the code in the second question is missing the int
in both cases, but adding it makes it OK, i.e.:
class A
{
public:
static int MaxHP;
};
int A::MaxHP = 23;
class Cat: A
{
public:
static const int MaxHP = 100;
};
works fine and with different values for A::MaxHP and Cat::MaxHP -- in this case the subclass is "not inheriting" the static from the base class, since, so to speak, it's "hiding" it with its own homonymous one.