Struggling with error message undefined reference to `Fish::Fish(std::string)' - c++

Question

I have this UML Diagram and I have written the code below but I am struggling with an error message
However, while compiling and linking, I got an error
/tmp/cc9oQaPX.o: In function `main':
main.cpp:(.text+0x8c): undefined reference to `Fish::Fish(std::string)'
main.cpp:(.text+0xe5): undefined reference to `Cat::Cat(std::string)'
main.cpp:(.text+0x116): undefined reference to `Fish::Fish()'
main.cpp:(.text+0x158): undefined reference to `Cat::Cat()'
collect2: error: ld returned 1 exit status
#include <iostream>
using namespace std;
class Animal // define base class
{
protected:
int legs; // base class properties
public:
Animal(int legNumbers) // set values of leg
{
legNumbers = legs; // set values of leg
}
virtual void eat() = 0; // method of base class
virtual void walk() {}; // method of base class
};
class Pet // define the pet class
{
protected:
string name; // set properties of pet class
public:
virtual string getName(); // define method
virtual string setName(string name); // set name values
virtual void play() // define play method
{
cout << " garfield is playing now." << endl; // out values
}
};
class Spider :public Animal //child class inherit base class
{
public:
Spider() :Animal(8) // spider class inherit animal class
{
cout << "animals with " << legs << " legs is walking. " << endl;
}
virtual void eat() // define virtual method
{
cout << "spider is eating now. " << endl;
}
};
class Cat :public Pet, public Animal // cat inherit two classes
{
public:
Cat(string name); // set name method
Cat();
virtual void play() // define method
{
cout << name << " is playing now. " << endl;
}
virtual void eat(); // define method here
};
class Fish : public Pet, public Animal // fish inherit two method
{
public: // define public members
Fish(string name);
Fish();
virtual void play()
{
cout << name << " is playing now. " << endl;
}
virtual void eat(); // method here
void walk()
{
cout << " Fish cannot walk " << endl; // output the values
}
};
string Pet::getName() // get name value from parent class
{
return string();
}
string Pet::setName(string name)
{
return string();
}
int main(int argc, char* argv[]) // define main method
{
Fish* f = new Fish("Jaws");
Cat* c = new Cat("Tenkir");
Animal *a = new Fish();
Animal* e = new Spider();
Pet* p = new Cat();
f->play();
c->play();
e->eat();
e->walk();
a->walk();
p->play();
return 0;
}

Answer 1

This is right code.
Firstly, you didn't defined the constructors for Cat an Fish
But that wasn't the only problem.
Your functions walk, eat, play need to be override. And eat() has to have a block, becuase in the base class (Animal) is deleted, like eat() = 0;
#include <iostream>
using namespace std;
class Animal // define base class
{
protected:
int legs; // base class properties
public:
Animal(int legNumbers) // set values of leg
{
legs = legNumbers; // set values of leg
}
virtual ~Animal() {}
virtual void eat() = 0; // method of base class
virtual void walk() {}; // method of base class
};
class Pet // define the pet class
{
protected:
string name; // set properties of pet class
public:
virtual string getName(); // define method
virtual void setName(string name); // set name values
virtual void play() // define play method
{
cout << " garfield is playing now." << endl; // out values
}
};
string Pet::getName() // get name value from parent class
{
return this->name;
}
void Pet::setName(string name)
{
this->name = name;
}
class Spider :public Animal //child class inherit base class
{
public:
Spider() :Animal(8) // spider class inherit animal class
{
cout << "animals with " << legs << " legs is walking. " << endl;
}
virtual void eat() // define virtual method
{
cout << "spider is eating now. " << endl;
}
};
class Cat :public Pet, public Animal // cat inherit two classes
{
public:
Cat(string name)
:Animal(4)
{
this->setName(name);
} // set name method
Cat():Animal(4){}
~Cat() override {}
virtual void play() override // define method
{
cout << name << " is playing now. " << endl;
}
virtual void eat() override {} // define method here
};
class Fish : public Pet, public Animal // fish inherit two method
{
public: // define public members
Fish(string name)
:Animal(0)
{
this->setName(name);
}
Fish():Animal(0){}
~Fish() override {}
virtual void play() override
{
cout << name << " is playing now. " << endl;
}
virtual void eat() override {} // method here
void walk() override
{
cout << " Fish cannot walk " << endl; // output the values
}
};
int main(int argc, char* argv[]) // define main method
{
Fish* f = new Fish("Jaws");
Cat* c = new Cat("Tenkir");
Animal *a = new Fish();
Animal* e = new Spider();
Pet* p = new Cat();
f->play();
c->play();
e->eat();
e->walk();
a->walk();
p->play();
return 0;
}