C/C++类型转换和异常处理

一，C/C++类型转换， 继承的使用

分为四种类型
1，static_cast
2，reinterpret_cast
3，dynamic_cast 使用在继承中
4，const_cast 改数值的

下面是具体的使用情况

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>#include <stdlib.h>#include <string.h>#include <iostream>using namespace std;class Animal{public:    Animal()    {}    ~Animal()    {}    virtual void cry() = 0;private:};class Dog : public Animal{public:    virtual void cry()    {        cout << "dkfdk" << endl;    }    void doHome()    {        cout << "2222222" << endl;    }};class Cat : public Animal{public:    virtual void cry()    {        cout << "333" << endl;    }    void doHome()    {        cout << "Cat " << endl;    }};void playOBj(Animal *base){    base->cry(); // 有继承， 和多态    //C++的类型的识别    //dynamic_cast 运行时类型识别    Dog *pDog =dynamic_cast<Dog *>(base);    if (pDog != NULL)    {        pDog->doHome(); //dog的工作    }    Cat *pCat = dynamic_cast<Cat *>(base);    if (pCat != NULL)    {        pCat->doHome();    }}void printBuf(const char *p){    char *p1 = NULL;    p1 = const_cast<char *>(p);    p1[0] = 'Z';    cout << p << endl;}int main(void){    double dp1 = 3.1415926;    //C类型转换    int num = (int)dp1;    //C++静态类型转换  编译的时    int num2 = static_cast<int>(dp1);    int num3 = dp1; //C语言中  隐式转换 都可以使用static_cast转换    //char* ====> int*    //C++    reinterpret_cast 不同类型的转换    char *p1 = "hello world !";    int *p2 = NULL;    p2 = reinterpret_cast<int *>(p1);    cout << "p1: " << p1 << endl;    cout << "p2: " << p2 << endl;    //总结：通过上面C类型转换的替代了    //C++    Cat c;   //向下转型    playOBj(&c);    //buf必须是可改的  数组的    char buf[] = "chenli";    printBuf(buf);    printf("\n");    system("pause");    return 0;}

二，异常处理的

1，异常的按照类型补获得

(…) 这个是获取所有的异常

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>#include <stdlib.h>#include <string.h>#include <iostream>using namespace std;void mycatch(int x, int y){    if (y == 0)    {        throw y;    }    cout << x / y << endl;}void myDirde(int x,int y){    mycatch(x, y);}int main(void){    try    {        mycatch(4, 4);        mycatch(4, 0);    }    catch (int e)    {        cout << "0错误" << endl;    }    catch (...)    {        cout << "程序错误" << endl;    }    printf("\n");    system("pause");    return 0;}

3，异常接口声明

1，抛出int，char类型的异常
void fcun() throw (int , char){}
2，抛出所有类型异常
void fcun() throw(){}

3,
throw “抛出char类型异常”

**结论1，：如果 接受异常的时候， 使用一个异常变量， copy构造异常变量

结论2,使用引用的话 throw时候的那个对象

结论3：指针可以和引用/元素写在一块 ， 但是引用和元素不能一起使用
**

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>#include <stdlib.h>#include <string.h>#include <iostream>using namespace std;//重点异常处理class BadSrcType {};class BadDecType {};class BadProcessType {public:    BadProcessType()    {        cout << "1111" << endl;    }    BadProcessType()    {        cout << "~~~~~~~~~1111";    }};int my_strcpy(char *tc, char *from){    if (from == NULL)    {        //异常处理        throw BadProcessType();    }    if (tc == NULL)    {        return 2;    }    if (*from == 'a')    {        return 3;    }    while (*from != '\0')    {        *tc = *from;        tc++;        from++;    }    return 0;}int main(void){    int ret = 0;    char buf1[] = "dfd";    char buf2[1024];    ret = my_strcpy(buf2, buf1);    if (ret != 0)    {        switch (ret)        {        case 1:            cout << "buf1错误" << endl;            break;        case 2:            cout << "buf2 错误" << endl;            break;        case 3:            cout << "未知错误" << endl;            break;        default:            break;        }    }    printf("\n");    system("pause");    return 0;}

4,异常在框架的使用案例

内部类的使用

没有优化的代码

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>#include <stdlib.h>#include <string.h>#include <iostream>using namespace std;class MyArray{public:    MyArray(int len);    int& operator[](int index);    int getLen();    ~MyArray();    //内部类   异常处理    class eNegative {};    class eZero{};    class eTooBig {};    class eTooSmall {};    class eSize {};private:    int *m_space;    int m_len;};MyArray::MyArray(int len){    if (len < 0)    {        throw eNegative();  // 抛出异常    }    else if (len == 0)    {        throw eZero();    }    else if (len > 1000)    {        throw eTooBig();    }    else if (len < 3)    {        throw eTooSmall();    }    this->m_len = len;    this->m_space = new int[len];}int & MyArray::operator[](int index){    return m_space[index];}int MyArray::getLen(){    return this->m_len;}MyArray::~MyArray(){    if (this->m_space != NULL)    {        delete[] this->m_space;        this->m_space = NULL;        this->m_len = 0;    }}int main(void){    try    {        MyArray a(5);        MyArray b(-5);        int i;        for (i = 0; i < a.getLen(); i++)        {            a[i] = i + 1;            printf("%d\n", a[i]);        }    }    catch (MyArray::eNegative e)  //类内类    {        cout << "eNegative 异常" << endl;    }    catch (MyArray::eSize e)  //类内类    {        cout << "eSize 异常" << endl;    }    catch (MyArray::eTooBig e)  //类内类    {        cout << "eTooBig 异常" << endl;    }    catch (MyArray::eTooSmall e)  //类内类    {        cout << "eTooSmall 异常" << endl;    }    catch (MyArray::eZero e)  //类内类    {        cout << "eZero 异常" << endl;    }    catch (...)    {        cout << "..." << endl;    }    printf("\n");    system("pause");    return 0;}

优化后
加入多态的继承的使用

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>#include <stdlib.h>#include <string.h>#include <iostream>using namespace std;class MyArray{public:    MyArray(int len);    int& operator[](int index);    int getLen();    ~MyArray();    //内部类   异常处理   继承    class eSize    {    public:        eSize(int size)        {            this->m_size = size;        }        virtual void printErr()        {            cout << "eSize--->size:" << this->m_size << " ";        }    protected:        int m_size;    };    class eNegative : public eSize    {    public:         eNegative(int size) :eSize(size)        {        }        virtual void printErr()        {            cout << "eNegative--->size:" << this->m_size << " ";        }    };    class eZero : public eSize    {    public:        eZero(int size) :eSize(size)        {        }        virtual void printErr()        {            cout << "eZero--->size:" << this->m_size << " ";        }    };    class eTooBig : public eSize    {    public:        eTooBig(int size) :eSize(size)        {        }        virtual void printErr()        {            cout << "eTooBig--->size:" << this->m_size << " ";        }    };    class eTooSmall : public eSize    {    public:        eTooSmall(int size) :eSize(size)        {        }        virtual void printErr()        {            cout << "eTooSmall-->size:" << this->m_size << " ";        }    };private:    int *m_space;    int m_len;};MyArray::MyArray(int len){    if (len < 0)    {        throw eNegative(len);  // 抛出异常    }    else if (len == 0)    {        throw eZero(len);    }    else if (len > 1000)    {        throw eTooBig(len);    }    else if (len < 3)    {        throw eTooSmall(len);    }    this->m_len = len;    this->m_space = new int[len];}int & MyArray::operator[](int index){    return m_space[index];}int MyArray::getLen(){    return this->m_len;}MyArray::~MyArray(){    if (this->m_space != NULL)    {        delete[] this->m_space;        this->m_space = NULL;        this->m_len = 0;    }}int main(void){    try    {        MyArray a(5);        MyArray b(-5);        int i;        for (i = 0; i < a.getLen(); i++)        {            a[i] = i + 1;            printf("%d\n", a[i]);        }    }    //多态的使用    MyArray::eSize &e    catch (MyArray::eSize &e)    {        cout << "len的大小" << endl;        e.printErr();    }    catch (...)    {        cout << "..." << endl;    }    printf("\n");    system("pause");    return 0;}

5,C++中库文件的异常处理

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>#include <stdlib.h>#include <string.h>#include <iostream>//C++异常处理库 #include <stdexcept>using namespace std;class Myexception : public exception{public:    Myexception(const char *p) :exception(p)    {        this->p = p;    }    virtual const char * what()    {        return p;    }private:    const char *p;};void setAge(int age){    if (age > 100)    {        throw out_of_range("您输入的年龄太大！！！");    }}int main(void){    try    {        setAge(111);    }    catch (out_of_range e)    {        cout << e.what() << endl;    }    //2,    try    {        throw Myexception("ckfjdkdkf");    }    catch (exception &e)    {        cout << e.what() << endl;    }    catch (...)    {        cout << "chnfd throw " << endl;    }    printf("\n");    system("pause");    return 0;}