Can someone tell what's wrong with my code? - c++

Question

I am a beginner and just can't figure out what am I doing wrong in this code. The result ends in a infinite loop (I think), that prints nothing. I intentionally left function speak() non-virtual and I know I'll only get Animal's data printed.
#include <iostream>
#include <string>
using namespace std;
class Animal
{
protected:
string m_name;
string m_speak;
public:
Animal(string name, string speak = "???"): m_name(name), m_speak(speak){}
string speak(){cout << m_name << " speaks " << m_speak;}
};
class Dog: public Animal
{
private:
string m_dspeak;
public:
Dog(string name, string speak = "Woof!"): Animal(name), m_dspeak(speak){}
string speak(){cout << m_name << " speaks " << m_dspeak;}
};
class Cat: public Animal
{
private:
string m_cspeak;
public:
Cat(string name, string speak = "Meow!"): Animal(name), m_cspeak(speak){}
string speak(){cout << m_name << " speaks " << m_cspeak;}
};
int main()
{
Cat Fred("Fred");
Dog Stuffy("Stuffy");
Animal *ptr = &Fred;
cout << ptr->speak() << endl;
Animal *ptr2 = &Stuffy;
cout << ptr2->speak() << endl;
}
Can someone help? I may did a very silly mistake here. Please tell me what's wrong?

Answer 1

In your code, you have made two major mistakes.
In the classes Animal, Dog and Cat you have three speak functions. But you declared them as string type functions. But the only output some text but does not return anything. You have to change them to void. Or you can return the text instead of outputing it.
In the main function you have written cout << ptr->speak() << endl; to output the text. But your speak function does not return any string to output. It outputs the text itself. So, you have to write ptr->speak(); to output the speech of the animal. You don't need cout there.
I have given two sample codes below. You can choose either of them. Both works just fine.
Sample #1: using void (no cout in main)
#include <iostream>
#include <string>
using namespace std;
class Animal
{
protected:
string m_name;
string m_speak;
public:
Animal(string name, string speak = "???"): m_name(name), m_speak(speak){}
void speak(){cout << m_name << " speaks " << m_speak;}
};
class Dog: public Animal
{
private:
string m_dspeak;
public:
Dog(string name, string speak = "Woof!"): Animal(name), m_dspeak(speak){}
void speak(){cout << m_name << " speaks " << m_dspeak;}
};
class Cat: public Animal
{
private:
string m_cspeak;
public:
Cat(string name, string speak = "Meow!"): Animal(name), m_cspeak(speak){}
void speak(){cout << m_name << " speaks " << m_cspeak;}
};
int main()
{
Cat Fred("Fred");
Dog Stuffy("Stuffy");
Animal *ptr = &Fred;
ptr->speak();
Animal *ptr2 = &Stuffy;
ptr2->speak();
}
Sample #2: using return in functions and cout in main
#include <iostream>
#include <string>
using namespace std;
class Animal
{
protected:
string m_name;
string m_speak;
public:
Animal(string name, string speak = "???"): m_name(name), m_speak(speak){}
string speak(){return m_name + " speaks " + m_speak;}
};
class Dog: public Animal
{
private:
string m_dspeak;
public:
Dog(string name, string speak = "Woof!"): Animal(name), m_dspeak(speak){}
string speak(){ return m_name + " " + m_speak;}
};
class Cat: public Animal
{
private:
string m_cspeak;
public:
Cat(string name, string speak = "Meow!"): Animal(name), m_cspeak(speak){}
string speak(){ return m_name + " speaks " + m_cspeak;}
};
int main()
{
Cat Fred("Fred");
Dog Stuffy("Stuffy");
Animal *ptr = &Fred;
cout << ptr->speak() << endl;
Animal *ptr2 = &Stuffy;
cout << ptr2->speak() << endl;
}

Answer 2

Change your two implementations of speak() to be something like this:
string speak(){ return m_name + " speaks " + m_speak; }
Currently, your speak methods don't have a return statement, so the return value is undefined, which could cause weird problems.

Answer 3

I am sorry I misunderstood your question. I edited the answer.
You do not need to cout in the function. You would do that in main.
#include <iostream>
#include <string>
using namespace std;
class Animal
{
protected:
string m_name;
string m_speak;
public:
Animal(string name, string speak = "???"): m_name(name), m_speak(speak){}
string speak(){return m_name + " speaks " + m_speak;}
};
class Dog: public Animal
{
private:
string m_dspeak;
public:
Dog(string name, string speak = "Woof!"): Animal(name), m_dspeak(speak){}
string speak(){ return m_name + " " + m_speak;}
};
class Cat: public Animal
{
private:
string m_cspeak;
public:
Cat(string name, string speak = "Meow!"): Animal(name), m_cspeak(speak){}
string speak(){ return m_name + " speaks " + m_cspeak;}
};
int main()
{
Cat Fred("Fred");
Dog Stuffy("Stuffy");
Animal *ptr = &Fred;
cout << ptr->speak() << endl;
Animal *ptr2 = &Stuffy;
cout << ptr2->speak() << endl;
}