異常的層次結構(繼承在異常中的應用)-傳智掃地僧課程案例

案例：設計一個數組類 MyArray，重載[]操作，
數組初始化時，對數組的個數進行有效檢查
1） index<0 拋出異常eNegative
2） index = 0 拋出異常 eZero
3）index>1000拋出異常eTooBig
4）index<10 拋出異常eTooSmall
5）eSize類是以上類的父類，實現有參數構造、並定義virtual void printErr()輸出錯誤。

// exception02.cpp: 定義控制檯應用程序的入口點。
//

#include "stdafx.h"
#include <iostream>
using namespace std;

class MyArray {

public:
    MyArray(int len);
    ~MyArray() ;

    class eSize {
    public:
        eSize(int size) {
            e_size = size;
        }
        virtual void printErr()=0;
    protected:
        int e_size;
    };

    class eNegative :public eSize {
    public:
        eNegative(int size) :eSize(size) {
            cout << "eNegative構造函數" << endl;
        }
        void printErr() {
            cout << "index<0" << endl;
        }
    };

    class eZero :public eSize {
    public:
        eZero(int size) :eSize(size) {
            cout << "eZero構造函數" << endl;
        }
        void printErr() {
            cout << "index=0" << endl;
        }
    };

    class eTooBig :public eSize {
    public:
        eTooBig(int size) :eSize(size) {
            cout << "eTooBig構造函數" << endl;
        }
        void printErr() {
            cout << "index>1000" << endl;
        }
    };

    class eTooSmall :public eSize {
    public:
        eTooSmall(int size) :eSize(size) {
            cout << "eTooSmall構造函數" << endl;
        }
        void printErr() {
            cout << "index<10" << endl;
        }
    };

public:
    int& operator[](int index) {
        return m_arr[index];
    }

private:
    int m_size;
    int *m_arr;

};

MyArray::MyArray(int len)
{
    if (len < 0)
        throw eNegative(len);
    if (len == 0)
        throw eZero(len);
    if (len > 1000)
        throw eTooBig(len);
    if (len>0&&len < 10)
        throw eTooSmall(len);
    m_size = len;
    m_arr = new int[m_size];
}
MyArray::~MyArray()
{
    if (m_arr != NULL)
    {
        delete[] m_arr;
        m_arr = NULL;
        m_arr = 0;
    }
}

int main(){
    try
    {
        MyArray test1(1001);
    }
    //多態
    /*
        catch (MyArray::eSize &e)
    {
        e.printErr();
    }
    */
    catch (MyArray::eNegative &e)
    {
        e.printErr();
    }
    catch (MyArray::eZero &e)
    {
        e.printErr();
    }
    catch (MyArray::eTooBig &e)
    {
        e.printErr();
    }
    catch (MyArray::eTooSmall &e)
    {
        e.printErr();
    }
    return 0;
}