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学习日记|C++中static_cast和dynamic_cast
//两种类型转换用于处理类之间的转换，dynamic_cast只能在多态中的使用（有虚函数）
/*
总结：
1 上行指针向下转
static不报错，编译通过，运行时不报错
dynamic，编译通过，运行时根据对象会报错2 子类指针向上转
符合继承关系，都成功
3 胡乱转
dynamic运行时报错，static编译不通过
*/
namespace C7N2_Cast
{
//class base
class base
{
public:
virtual void vFunc()
{
cout << "base vFunc" << endl;
cout << str << endl;
}
void print()
{
cout << str << endl;
}
base()
{
str = "base";
}
private:
string str;
};
//class derive1 :public base
class derive1 :public base
{
public:
virtual void vFunc()
{
cout << "derive1 vFunc" << endl;
cout << str << endl;
}
void print()
{
cout << str << endl;
}
derive1()
{
str = "derive1";
}
private:
string str;
};
//class derive2 :public base
class derive2 :public base
{
public:
virtual void vFunc()
{
cout << "derive2 vFunc" << endl;
cout << str << endl;
}
void print()
{
cout << str << endl;
}
derive2()
{
str = "derive2";
}
private:
string str;
};
void test()
{
base b1, *pbb,*pbd;
derive1 d1, *pdd, *pdb;
pbb = &b1;
pbd = &d1;
pdd = &d1;
//pdb = &b1;
//error:子类指针不能指向父类对象//dynamic_cast
//1.1 上行指针 向下转
//对象符合-->成功
if (dynamic_cast(pbd) == nullptr) {
cout << "dynamic_cast(pbd)时失败" << endl;
}
//对象不符合-->失败
if (dynamic_cast(pbd) == nullptr) {
cout << "dynamic_cast(pbd)时失败" << endl;
//失败
}
//1.2 子类指针向上转
//符合继承关系-->成功
if (dynamic_cast(pdd) == nullptr) {
cout << "dynamic_cast(pdd)时失败" << endl;
}
//1.3 胡乱转
//不满足继承关系-->失败
if (dynamic_cast(pdd) == nullptr) {
cout << "dynamic_cast(pdd)时失败" << endl;
//失败
}//static_case
//2.1 上行指针向下转
//对象符合-->成功
if (static_cast(pbd) == nullptr) {
cout << "static_cast(pbd)时失败" << endl;
}
//对象不符合-->不报错
if (static_cast(pbd) == nullptr) {
cout << "static_cast(pbd)时失败" << endl;
}
//2.2 子类指针 向上转
//符合继承关系-->成功
if (static_cast(pdd) == nullptr) {
cout << "static_cast(pdd)时失败" << endl;
}
//不符合继承关系-->编译不通过
//if (static_cast(pdd) == nullptr) {
//cout << "static_cast(pdd)时失败" << endl;
//没有类型检查
//}
//2.3 胡乱转
//编译都不通过 }
}
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