CODEWITHSUNDEEP
c++classoopinheritancevirtual
Yoav Linder
Yoav Linder

Reputation: 123

How can I override a virtual function in a derived class?

I am trying to build a zoo for practicing c++ and oop. I have made 2 classes, Animal class (the base class) and Bear class (the derived class). I want to have 2 virtual functions in Animal that I will override in Bear but CLION tells me that 'Function Walk did not decleared in class Bear'.

What do I need to change?

This is the base class (Animal) header:

class Animal {
public:
    Animal();
    Animal(string Name, int CageNum, string FoodType, string Gender, bool NeedTreatment);

    virtual void Talk() = 0;
    virtual void Walk();
    int CageNum;
    string FoodType;
    string Gender;
    bool NeedTreatment;
    string Name;
};

CPP:

Animal::Animal() {};
Animal::Animal(string Name, int CageNum, string FoodType, string Gender, bool NeedTreatment) :
        Name(Name), CageNum(CageNum), FoodType(FoodType), Gender(Gender), NeedTreatment(NeedTreatment){};

This is the derived class (Bear) header:

#include "Animal.h"

class Bear : public Animal{
protected:
    string FurColor;
public:
    Bear(string Name, int CageNum, string FoodType, string Gender, bool NeedTreatment,string FurColor);

};

and this is the CPP:

#include "Bear.h"
Bear::Bear(string Name, int CageNum, string FoodType, string Gender, bool NeedTreatment,string FurColor) :
        Animal(Name, CageNum, FoodType, Gender, NeedTreatment),FurColor(FurColor) {};
void Bear::Walk() {
    cout << "Bear Moves";
}
void Animal::Talk() {
    "Bear Noise";
}

Upvotes: 4

Views: 1709

Answers (1)

πάντα ῥεῖ
πάντα ῥεῖ

Reputation: 1

If you define a function like

void Bear::Walk() {
    cout << "Bear Moves";
}

its declaration must appear in the class definition:

class Bear : public Animal{
protected:
    string FurColor;
public:
    Bear(string Name, int CageNum, string FoodType, string Gender, bool NeedTreatment,string FurColor);
    void Walk() override; // <<<<<<<<<<<<<<<<<<
};

Alternatively you can omit the definition, and the base class member definition Animal::Walk() will be used.

Also

void Animal::Talk() {
    "Bear Noise";
}

is wrong (or at last doesn't do what is intended).

A pure virtual function like Talk() from the base class, must have a declaration and definition in the Bear class, unless the class is intentionally left abstract.

class Bear : public Animal{
protected:
    string FurColor;
public:
    Bear(string Name, int CageNum, string FoodType, string Gender, bool NeedTreatment,string FurColor);
    void Talk() override; // <<<<<<<<<<<<<<<<<<
    void Walk() override;
};

and the definition

void Bear::Talk() {
    "Bear Noise";
}

Upvotes: 3

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