4elist1905.cpp

《21天学通C＋＋》附盘的原代码。书上的每个例子在这里都有相应的C语言程序。

//Listing 19.5 Passing Template Objects to and from Functions
#include <iostream>
using namespace std;

const int DefaultSize = 10;

// 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)\n";
}

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

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

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

	Array& operator=(const Array&);
	T& operator[](int offSet) { return pType[offSet]; }
	const T& operator[](int offSet) const
		{ return pType[offSet]; }
	int GetSize() const { return itsSize; }

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

private:
	T *pType;
	int  itsSize;
};

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;
}

// implementations follow...

// implement the 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];
}

void IntFillFunction(Array<int>& theArray);
void AnimalFillFunction(Array<Animal>& theArray);

int main()
{
	Array<int> intArray;
	Array<Animal> animalArray;
	IntFillFunction(intArray);
	AnimalFillFunction(animalArray);
	cout << "intArray...\n" << intArray;
	cout << "\nanimalArray...\n" << animalArray << endl;
	return 0;
}

void IntFillFunction(Array<int>& theArray)
{
	bool Stop = false;
	int offset, value;
	while (!Stop)
	{
		cout << "Enter an offset (0-9) ";
		cout << "and a value. (-1 to stop): " ;
		cin >> offset >> value;
		if (offset < 0)
			break;
		if (offset > 9)
		{
			cout << "***Please use values between 0 and 9.***\n";
			continue;
		}
		theArray[offset] = value;
	}
}


void AnimalFillFunction(Array<Animal>& theArray)
{
	Animal * pAnimal;
	for (int i = 0; i<theArray.GetSize(); i++)
	{
		pAnimal = new Animal;
		pAnimal->SetWeight(i*100);
		theArray[i] = *pAnimal;
		delete pAnimal;  // a copy was put in the array
	}
}