Expert: Zlatko - 11/4/2011

Question
im writing a program trying learn c++ and i keep getting the error message, no appropriate constructor available.  can you help me understand what im doing wrong?  the purpose of this project is to:

For this assignment, you will implement a class, CPet, which will represent a pet. in so many words i need to prompt the user to give the pet name, the pet sound and make it sound 3 times.
this is what i have so far:

--------------------------------------------------------
// this is the CPet.h file
#include <string>
using namespace std;

// Pet class definition
class Pet
{ // start Pet class
public:
  Pet( string );
  void setPetType(string petTypeName);
  string getPetType();
  void displayMessage();

private:
  string PetType; // Name for this pet
};// end Pet class

-----------------------------------------------------------------

// this is my pet.cpp file
#include <iostream>
#include "Pet.h"  // include definition of class Pet
using namespace std;

Pet::Pet( string petTypeName )
{
  setPetType( petTypeName);
} // end Pet constructor

// function to set petTypeName
void Pet::setPetType(std::string petTypeName)
{
  PetType = petTypeName;
}

string Pet::getPetType()
{
  return PetType;
}
void Pet::displayMessage()
{
  cout << "Your pet is a\n" << getPetType()
     << "!" << endl;
} // end function displayMessage()



----------------------------------------------------------------
//this is my main.cpp file
#include <iostream>
#include "Pet.h"
using namespace std;

// functionmain begins program execution
int main()
{
  string nameOfPet;  
  Pet myPet;

  cout << "Your current pet type is: " << myPet.getPetType()
     << endl;

  cout << "\nPlease enter the type of pet: " << endl;
  getline( cin, nameOfPet );
  myPet.setPetType( nameOfPet );

  cout << endl;
  myPet.displayMessage();
}

Answer
Hi jwilson

In your main program, you have the line
Pet myPet;

That line is trying to make a Pet but it is not providing any parameters. The only constructor available to Pet is
Pet::Pet( string petTypeName )
which takes a string.

You should create another constructor in Pet which takes no arguments, and still initializes the Pet to something. For example

Pet::Pet()
{
   setPetType("");
}
The call to setPetType("") above is optional because the string class has its own default constructor which sets string objects to be empty.

If you don't provide any constructor, C++ will provide a default no-argument constructor which does nothing. As soon as you provide any constructor, C++ stops giving you the default. Your program may have compiled in the past, then stopped compiling when you added a constructor and C++ stopped giving you the default.

I hope that explains things.
Best regards
Zlatko