I have three classes structured like this:
#include <iostream>
using namespace std;
class Keyword
{
public:
virtual float GetValue() = 0;
};
class CharacterKeyword : public Keyword
{
public:
virtual float GetValue(){return _value;}
private:
float _value;
};
class MeasurementKeyword : public Keyword
{
public:
virtual float GetValue(){return _value;}
private:
float _value;
};
class AddressType : public CharacterKeyword, public MeasurementKeyword
{
private:
float address;
float addresExt;
};
int main()
{
AddressType *a = new AddressType();
a->GetValue();
return 0;
}
I am getting the following:
In function ‘int main()’:
error: request for member ‘GetValue’ is ambiguous
error: candidates are: virtual float Keyword::GetValue()
error: virtual float MeasurementKeyword::GetValue()
error: virtual float CharacterKeyword::GetValue()
I have done some reading into multiple inheritance and I know that it has a lot of pitfalls - this being one of them. I need my class structure to be like this so I was wondering if there was a way that I could fix this using templates?
Update
After reading your comments, my original thought was that maybe I can just delineate between an AddressType
that is a CharacterKeyword
and an AddressType
that is a MeasurementKeyword
by templating the AddressType
. And using it as such in the updated code. OR I can just specify the namespace of the member that I would like. Since the templated way has not been mentioned yet as an answer, is it a bad fix? Should I just specify the namespace of the member I want?
template <class T>
class AddressType : public T
{
private:
float address;
float addresExt;
};
int main()
{
AddressType<MeasurementKeyword> *a = new AddressType<MeasurementKeyword>();
a->GetValue();
return 0;
}
This is because of a diamond inheritance pattern, to resolve the error you can specify the specific namespace you want the member from like.
paddressType->MeasurementKeyword::GetValue()
or
paddressType->CharacterKeyword::GetValue()
AddressType
class has access to the GetValue
members from both the classes it inherits from and can't choose one (call is ambiguous). ::
) helps specify which one you actually want.