Declaring the templates in c++ - c++

Question

// stdafx.h
// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//
#include "targetver.h"
#include <stdio.h>
#include <tchar.h>
#include <iostream>
using namespace std;
#include "Animal.h"
// TODO: reference additional headers your program requires here
class Animal
{
private:
int itsWeight;
public:
Animal(int);
Animal();
~Animal() {}
int getWeight() const { return itsWeight; }
void Display() const;
};
template <class T>
class Array
{
private:
T *pType;
int itsSize;
const int defaultSize = 10;
public:
//constructors
Array(int itsSize = defaultSize);
Array(const Array &rhs);
~Array() { delete[] pType; }
//operators
Array& operator=(const Array&);
T& operator[](int offSet){ return pType[offSet]; }
const T& operator[](int offSet) const { return pType[offSet]; }
//methods of Access
int getSize() const { return itsSize; }
};
//constructor
template <class T>
Array<T>::Array(int size) :
itsSize(size)
{
pType = new T[size];
for (int i = 0; i < size; i++)
{
pType[i] = 0;
}
}
//copy-constructor
template <class T>
Array<T>::Array(const Array &rhs)
{
itsSize = rhs.getSize();
pType = new T[itsSize];
for (int i = 0; i < itsSize; i++)
{
pType[i] = rhs[i];
}
}
//operator prisvoeniya
template <class T>
Array<T>& Array<T>::operator=(const Array &rhs)
{
if (this == &rhs)
return *this;
delete[] pType;
itsSize = rhs.getSize();
pType = new T[itsSize];
for (int i = 0; i < itsSize; i++)
{
pType[i] = rhs[i];
}
return *this;
}
//this is the file "Animal.cpp"
#include "stdafx.h"
#include "Animal.h"
Animal::Animal()
{
itsWeight = 0;
}
Animal::Animal(int weight)
{
itsWeight = weight;
}
void Animal::Display() const
{
cout << itsWeight;
}
// the main function
#include "stdafx.h"
int_tmain(int argc, _TCHAR* argv[])
{
Array<int> theArray; //Integer array
Array<Animal> theZoo; //Animal array
Animal *pAnimal;
//filling the array
for (int i = 0; i < theArray.getSize(); i++)
{
theArray[i] = i * 2;
pAnimal = new Animal[i * 3];
theZoo[i] = *pAnimal;
delete pAnimal;
}
for (int j = 0; j < theArray.getSize(); j++)
{
cout << "theArray[" << j << "]:\t";
cout << theArray[j]<<"\t\t";
cout << "theZoo[" << j << "]:\t";
theZoo[j].Display();
cout << endl;
}
return 0;
}
The problem is that: The compiler gives me the errors
Error 1 error C2648: 'Array<int>::defaultSize' : use of member as default parameter requires static member
d:\documents\work\c++ files\tigrans\homework10\templates\templates\templates\animal.h 28 1 Templates
Error 2 error C2648: 'Array<Animal>::defaultSize' : use of member as default parameter requires static member
d:\documents\work\c++ files\tigrans\homework10\templates\templates\templates\animal.h 28 1 Templates
Anybody can help me to understand that. I change the
const int defaultSize=10;
to
static const int defaultSize=10
then there is not errors but in that time show Debug Assertion Failed!

Answer 1

This part of your code is dodgy
{
pAnimal = new Animal[i * 3];
theZoo[i] = *pAnimal;
delete pAnimal;
}
The first line allocates an array of i*3 Animals, using their default constructor (which makes an Animal with itsWeight=0). In the second line you assign the first these newly allocated Animals to theZoo[i]. Finally, the third line tries to de-allocate the Animals.
The last line contains an error, since you call delete on a pointer obtained with new [].
The whole concept of creating objects on the heap only to immediately destroy them is quite dubious -- perhaps you come from another programming language, where this is the only way to create things? First, you could simply use an automatic variable
{
Animal a; // or a(i*3);
theZoo[i] = a;
}
or yet briefer
{
theZoo[i] = Animal(i*3);
}
(Note the if you would use a std container, you could say theZoo.emplace_back(i*3);, avoiding the copy of Animal.)