Class objects in main

[bailey]

Hi,

I need to make an object for a class in main in a piece of code that I am compiling. However it won't let me create this object, similar to how I've done it with other classes. It's coming up with:

error: no matching function for call to 'class::class()'
note: candidates are: class::class(std::vector<double, std::allocator<double> >, std::vector<double, std::allocator<double> >, double, double, double)
class::class(const CorrBinModel&)

Can anybody suggest any reasons why this might be? This is a really frustrating problem and has been holding me back for a while so any help would be much appreciated. Will provide code if required. Thanks in advance.

[Peter87]

You are trying to create the object using the default constructor (constructor with that takes no arguments). The class doesn't have a default constructor so it fails to compile. If you want the class to have a default constructor you have to create one, otherwise you have to use one of the constructors that do exist.

[bailey]

Thanks very much, there is a constructor in the class already that I'm not using for anything. Should I just leave it blank? This is how I have it now although I didn't really know how to use it.

/class::class(vector<double> _A, vector<double> _B, double _C, double _D, double _E)
{
    A=_A;
   B=_B;
    C=_C;
    D=_D;
    E=_E;

}

[bailey]

This seems to be the only thing holding back my code. I have tried deleting the constructor and changing it to use the default constructor, however I've not had any luck so far. Any ideas would be much appreciated?

[Gaminic]

Can you show us the code in Main?

[bailey]

/using namespace std;

int main()
{
    double E, F;
    int G;
    class MyModel;
    if (MyModel.G()==1) return 1;
    M MyOption1;

P(MyModel,MyOption1,E,F,G) << endl; 

    return 0;
}

[zb0S216C]

class cannot be used as an identifier since it's a reserved word.

_Wazzak

[bailey]

Thank you I have changed that, however it is still causing the same problem.

[Lowest0ne]

You need something like this:

vector<double> _A, _B;
double _C, _D, _E;

// Initialize these variables

MyModel myModel(_A, _B, _C, _D, _E);

Then members of myModel can be accessed.

I also highly recommend changing your variable names to mean something. You can also keep each one the same:

#include <iostream>
using namespace std;

class Refrigerator 
{
private:
  int amountOfEggs;

public:
  // Default constructor
  Refrigerator()
    :amountOfEggs(0)
    {
    };
  // Custom constructor
  Refrigerator(int amountOfEggs)
    :amountOfEggs(amountOfEggs)
    {
    };

   //Accessor
   int getAmountOfEggs(){ return amountOfEggs;}

};


int main(){
  int amountOfEggs = 12;
  Refrigerator yourFridge, myFridge(amountOfEggs);

  cout << "You have: " << yourFridge.getAmountOfEggs() << " eggs.\n";
  cout << "I have: " << myFridge.getAmountOfEggs() << " eggs.";
  cin.get();
  return 0;
} 

[bailey]

Ok slightly different question as I think I have solved the problem I was having initially. It concerns the object of a virtual function. I am getting this error message. I have seen a similar piece of code which I have adapted to suit my purposes. However I am receiving this error message which wasn't received before and I cannot see what the difference is. Would anyone be able to tell me why I might get this type of error?

error: cannot declare variable 'C' to be of abstract type 'M'|
note: because the following virtual functions are pure within 'M':|
note: virtual double Rectangle::P(double)

[doug4]

You have code structured something along these lines.

class Rectangle
{
public:
	virtual double P(double x) = 0;
};

class M : public Rectangle
{
};

int main()
{
	M c;
	return 0;
}

The function Rectangle::P() has no definition (called "pure virtual", designated by "= 0"), so it is an abstract class. Abstract classes cannot be instantiated. You must declare a subclass and define the pure virtual functions (P in this case) in order to instantiate a derived object with a base class of Rectangle.

To fix your problem, declare and define: double M::P(double);