Not calling base class constructor from derived class
15,098
Solution 1
Make an additional empty constructor.
struct noprapere_tag {};
class baseClass
{
public:
baseClass() : x (5), y(6) { };
baseClass(noprapere_tag) { }; // nothing to do
protected:
int x;
int y;
};
class derClass : public baseClass
{
public:
derClass() : baseClass (noprapere_tag) { };
};
Solution 2
A base class instance is an integral part of any derived class instance. If you successfully construct a derived class instance you must - by definition - construct all base class and member objects otherwise the construction of the derived object would have failed. Constructing a base class instance involves calling one of its constructors.
This is fundamental to how inheritance works in C++.
Solution 3
Sample working program
#include <iostream>
using namespace std;
class A
{
public:
A()
{
cout<<"a\n";
}
A(int a)
{}
};
class B:public A
{
public:
B() : A(10)
{
cout<<"b\n";
}
};
int main()
{
new A;
cout<<"----------\n";
new B;
return 0;
}
output
a
----------
b
Author by
Brad
Updated on June 16, 2022Comments
-
Brad about 2 years
Say I have a base class:
class baseClass { public: baseClass() { }; };
And a derived class:
class derClass : public baseClass { public: derClass() { }; };
When I create an instance of
derClass
the constructor ofbaseClass
is called. How can I prevent this?