CODEWITHSUNDEEP
c++derived-class
Elgirhath
Elgirhath

Reputation: 449

Derived class using variables from abstract base class C++

I created an abstract Light class with fields and methods common for all the lights and now I try to derive a Directional Light from it.

class Light
{
public:
    unsigned int strength;
    Color color;
    unsigned int index;

    Light() {};
    virtual ~Light() = 0;

    virtual pointLuminosity() = 0;
};

class DirectionalLight : public Light
{
public:
    Vector direction;
    DirectionalLight(const unsigned int &_strength, [...] ): strength(_strength), [...] {}
};

The above code results in an error:

error: class 'DirectionalLight' does not have any field named 'strength'

What is the proper way to derive all the fields from Light class and use them in the DirectionalLight objects?

Upvotes: 1

Views: 123

Answers (2)

kocica
kocica

Reputation: 6467

You can't do that in initializer list since strength is not member of DirectionalLight. You have to initialize derived member in the body of constructor or call base class constructor in the initializer list of the derived class constructor.

For example:

DirectionalLight(const unsigned int &_strength): { strength = _strength; }

Or:

Light(int _strength) : strength(_strength) {}
...
DirectionalLight(const unsigned int &_strength): Light(_strength) { }

Second option is prefered, also strength in Light should be protected, so the encapsulation is not destroyed.

Upvotes: 2

john
john

Reputation: 87944

You can use strength anywhere but an initialiser list. This works

DirectionalLight(const unsigned int &_strength) { strength = _strength; }

Alternatively you can add a constructor to Light

class Light
{
public:
    unsigned int strength;
    Light(unsigned s) : strength(s) {}
};

DirectionalLight(const unsigned int &_strength) : Light(_strength) {}

Upvotes: 4

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