more effective c++——Item M30 代理类（一）多维数组的实现

代理类：用一个类来实现我们所需要的而 C++语言中并没有提供的东西，用户并不需要该类的具体实现

总结：
1.模板类中，输入输出操作符重载不能在模板类外部实现
2.数组类需要提供基本的操作：单参构造，拷贝构造，赋值操作，输出操作符
3.n维数组类持有n-1维数组的二级指针
4.多维数组可以看作n-1维数组的叠加，构造时需要先构造row个n-1个维数组的指针，然后再次为这些指针分配空间，析构时先删除n-1维数组的内存，再删除存放指针的内存
5.不要模板类型——typename

一维数组的实现：

#pragma once#include <iostream>//#include <afx.h>using namespace std;template<typename T>class Array1D {public:    Array1D(const int size) :m_isize(size), m_array(new T[m_isize]) {}    ~Array1D() {        delete[] m_array;    }    Array1D<T> & operator=(const Array1D<T> &rhl);    const T & operator[](const int index) const;    T & operator[](const int index);    friend ostream &operator<< (ostream & os, const Array1D<T> &rhl)    {        for (int i = 0; i < rhl.m_isize; ++i)        {            cout << rhl[i];            if (i != rhl.m_isize - 1)            {                cout << "   ";            }        }        cout << endl;        return os;    }private:    int m_isize;    T *m_array;};template<typename T>inline Array1D<T> & Array1D<T>::operator=(const Array1D<T> &rhl){    if (m_array == rhl.m_array)    {        return *this;    }    delete[] m_array;    m_isize = rhl.m_isize;    m_array = new T[m_isize];    for (int i = 0;i < m_isize;++i)    {        m_array[i] = rhl.m_array[i];    }    return *this;}template<typename T>inline const T & Array1D<T>::operator[](const int index) const{    return m_array[index];}template<typename T>inline T & Array1D<T>::operator[](const int index){    return m_array[index];}inline void test_array1d(){    int isize = 10;    Array1D<int> arr1d(isize);    for (int i = 0; i < isize; ++i)    {        arr1d[i] = i * 2 + 1;    }    cout << arr1d;}

二维数组的实现：

#pragma once#include "Array1D.h"#include <iostream>using namespace std;template<typename T>class Array2D {public:    Array2D(const int row,const int col) :m_irow(row), m_icol(col) {        m_array = new Array1D<T> *[m_irow];        for (int i = 0; i < m_irow;++i)        {            m_array[i] = new Array1D<T>(m_icol);        }    }    ~Array2D() {        for (int i = 0; i < m_irow; ++i)        {            delete m_array[i];        }        delete[] m_array;    }    Array2D<T> & operator=(const Array2D<T> &rhl);    const Array1D<T> & operator[](const int index) const;    Array1D<T> & operator[](const int index);    friend ostream &operator<< (ostream & os, const Array2D<T> &rhl)    {        for (int i = 0; i < rhl.m_irow; ++i)        {            cout << rhl[i];        }        cout << endl;        return os;    }private:    int m_irow;    int m_icol;    Array1D<T>  **m_array;};template<typename T>inline Array2D<T> & Array2D<T>::operator=(const Array2D<T> &rhl){    if (m_array == rhl.m_array)    {        return *this;    }    for (int i = 0; i < m_irow; ++i)    {        delete m_array[i];    }    delete[] m_array;    m_irow = rhl.m_irow;    m_icol = rhl.m_icol;    m_array = new Array1D<T> *[m_irow];    for (int i = 0; i < m_irow; ++i)    {        m_array[i] = new Array1D<T>(m_icol);        *m_array[i] = *rhl.m_array[i];    }    return *this;}template<typename T>inline const Array1D<T> & Array2D<T>::operator[](const int index) const{    return *m_array[index];}template<typename T>inline Array1D<T> & Array2D<T>::operator[](const int index){    return *m_array[index];}inline void test_array2d(){    int row = 5;    int col = 7;    Array2D<int> arr2d(row,col);    for (int i = 0; i < row; ++i)    {        for (int j = 0 ;j < col;++j)        {            arr2d[i][j] = i + i*j;        }    }    cout << arr2d;}

三维数组的实现：

#pragma once#include "Array2D.h"#include <iostream>using namespace std;template<typename T>class Array3D {public:    Array3D(const int len, int wid, int hight) :m_len(len), m_wid(wid), m_hight(hight)    {        m_array = new Array2D<T> *[len];        for (int i = 0;i < len;++i)        {            m_array[i] = new Array2D<T>(wid, hight);        }    }    ~Array3D() {        for (int i = 0; i < m_len; ++i)        {            delete m_array[i];        }        delete[] m_array;    }    Array3D<T> & operator=(const Array3D<T> &rhl);    const Array2D<T> & operator[](const int index) const;    Array2D<T> & operator[](const int index);    friend ostream &operator<< (ostream & os, const Array3D<T> &rhl)    {        for (int i = 0; i < rhl.m_len; ++i)        {            cout << rhl[i];        }        cout << endl;        return os;    }private:    int m_len;    int m_wid;    int m_hight;    Array2D **m_array;};template<typename T>const Array2D<T> & Array3D<T>::operator[](const int index) const{    return *m_array[index];}template<typename T>inline Array2D<T>& Array3D<T>::operator[](const int index){    return *m_array[index];}template<typename T>inline Array3D<T>& Array3D<T>::operator=(const Array3D<T>& rhl){    if (m_array == rhl.m_array)    {        return *this;    }    for (int i = 0; i < m_len; ++i)    {        delete m_array[i];    }    delete[] m_array;    m_len = rhl.m_len;    m_wid = rhl.m_wid;    m_hight = rhl.m_hight;    m_array = new Array2D<T> *[m_len];    for (int i = 0; i < m_irow; ++i)    {        m_array[i] = new Array2D<T>(m_wid,m_hight);        *m_array[i] = *rhl.m_array[i];    }    return *this;}