Constructor with string (using char array) parameter - c++

Question

Just to make everyone aware. I have to use char array for strings, this is homework and has to be done that way. Also the classes are made on purporse.
I'm supposed to read a fish' name via my Fish class, which is a subclass of Animal class. If the input length is more than 0, then I'll run the constructor with the char array parameter and update the "fishname" inside Fish class. If not, I'll run the constructor without parameter (Fish() constructor).
My questions:
Right now it gives me the option to write in an input, I do that - it crashes. It is the Fish object causing it, but don't know why. How come?
How would I transport the data that I'll get into "fishname" in the Fish data, over to "name" in the Animal class?
So this is what I have made so far, but it only crashes after input.
#include
using namespace std;
#include <iostream>
using namespace std;
class Animal {
private:
char* name;
public:
Animal() { strcpy(name, ""); } // Constructors that set name to nothing
void writeName() { cout << name; } // Function to read an animal's name
};
class Fish : public Animal {
private:
char* fishname;
public:
Fish() {}
Fish(const char* name) { strcpy(fishname, name); }
};
int main() {
char fishname[20];
cout << "Read fish's name: "; cin.ignore();
cin.getline(fishname, 20);
if(strlen(fishname) > 0) Fish f1(fishname);
else Fish f1;
return 0;
}

Answer 1

About the best you can do, short of implementing a lot of the functionality of std::string is to use a fixed size char array. This is not generally a good practice. I would not usually do this, but I will take pity.
#include <iostream>
#include <cassert>
using namespace std; // NEVER write this in a header file. Just saying.
class Animal {
public:
static const int max_name = 128;
Animal() {
name[0] = 0;
}
void writeName() { cout << name; } // Function to read an animal's name
private:
char name[max_name];
};
class Fish : public Animal {
private:
char fishname[Animal::max_name];
public:
Fish() {
fishname[0] = 0;
}
Fish(const char* name) {
assert(strlen(name) < Animal::max_name);
strcpy(fishname, name);
}
};