list1907.cpp

teach yourself C++ in 21 days 第五版

#include <iostream>
using namespace std;

const int DefaultSize = 3;

// A trivial class for adding to arrays
class Animal
{
  public:
     // constructors
    Animal(int);
    Animal();
    ~Animal();

    // accessors
    int GetWeight() const { return itsWeight; }
    void SetWeight(int theWeight) { itsWeight = theWeight; }

    // friend operators
    friend ostream& operator<< (ostream&, const Animal&);

  private:
    int itsWeight;
};

// extraction operator for printing animals
ostream& operator<<
   (ostream& theStream, const Animal& theAnimal)
{
   theStream << theAnimal.GetWeight();
   return theStream;
}

Animal::Animal(int weight):
   itsWeight(weight)
{
   //cout << "animal(int) ";
}

Animal::Animal():
   itsWeight(0)
{
   //cout << "animal() ";
}

Animal::~Animal()
{
   //cout << "Destroyed an animal...";
}

template <class T>   // declare the template and the parameter
class Array          // the class being parameterized
{
  public:
    // constructors
    Array(int itsSize = DefaultSize);
    Array(const Array &rhs);
    ~Array() { delete [] pType;   itsNumberArrays--; }

    // operators
    Array& operator=(const Array&);
    T& operator[](int offSet) { return pType[offSet]; }
    const T& operator[](int offSet) const
    { return pType[offSet]; }
    // accessors
    int GetSize() const { return itsSize; }
    static int GetNumberArrays() { return itsNumberArrays; }

    // friend function
    friend ostream& operator<< (ostream&, const Array<T>&);

  private:
    T *pType;
    int  itsSize;
    static int itsNumberArrays;
};

template <class T>
int Array<T>::itsNumberArrays = 0;

template <class T>
Array<T>::Array(int size = DefaultSize):
   itsSize(size)
{
   pType = new T[size];
   for (int i = 0; i < size; i++)
      pType[i] = (T)0;
   itsNumberArrays++;
}

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];
}

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];
   itsNumberArrays++;
}

template <class T>
ostream& operator<< (ostream& output, const Array<T>& theArray)
{
   for (int i = 0; i < theArray.GetSize(); i++)
      output << "[" << i << "] " << theArray[i] << endl;
   return output;
}

int main()
{
   cout << Array<int>::GetNumberArrays() << " integer arrays\n";
   cout << Array<Animal>::GetNumberArrays();
   cout << " animal arrays" << endl << endl;
   Array<int> intArray;
   Array<Animal> animalArray;

   cout << intArray.GetNumberArrays() << " integer arrays\n";
   cout << animalArray.GetNumberArrays();
   cout << " animal arrays" << endl << endl;

   Array<int> *pIntArray = new Array<int>;

   cout << Array<int>::GetNumberArrays() << " integer arrays\n";
   cout << Array<Animal>::GetNumberArrays();
   cout << " animal arrays" << endl << endl;

   delete pIntArray;

   cout << Array<int>::GetNumberArrays() << " integer arrays\n";
   cout << Array<Animal>::GetNumberArrays();
   cout << " animal arrays" << endl << endl;
   return 0;
}