C中的几种类型转换const_cast，static_cast和dynamic_cast

freeeyes · 发表于 2015-12-31 08:50:57

首先声明两个类用于测试

#include<iostream>
using namespace std;
class Shape
{
public:
string name;
string *shape;
Shape(string name){
      this->shape = new string("a dynamic shape");
      this->name = name;
      cout<<name<<"is a Shape" << endl;
}
virtual void foo()
{
      cout <<" foo in shape" << endl;
}
virtual ~Shape(){
      delete this->shape;
      cout << this->name << "delete dynamic shape" << endl;
      cout<<this->name<<"is destoried as a shape"<<endl;
}
};
class Circle : public  Shape
{
public:
string *shape;
string name;
Circle(string name)
:Shape(name)
{
      this->shape = new string("dynamic circle");
      this->name = name;
      cout << name << "is a Circle"<< endl;
}
void foo()
{
      cout << "foo in circle" << endl;
}
~Circle()
{
      delete this->shape;
      cout << this->name << "delete dynamic circle" << endl;
      cout << name << "is destoried as a circle" << endl;
}
};

//测试代码
int main(void)
{
//const_cast用于去掉const关键字，
cout << "const_cast test" << endl;
const int* const a = new int(3);
cout << *a << endl;
int *b = const_cast<int*>(a);
*b = 5;
delete b;
cout << *a << endl;
cout << "const_cast test over" << endl;

//用static_cast把子类指针转化为父类指针，记得基类要虚析够哦
//否则容易造成内存泄漏。
cout << "static_cast test" << endl;
Shape *base = new Shape("b");
Circle* c= new Circle("c");
Shape* b1 = base;
Circle* c1;
base = static_cast<Shape*> (c);

delete base;
delete c;
cout << "static_cast text over"<< endl;

//dynamic_cast用于把基类指针转化为子类指针，失败返回null，用于运行时类型检查（是不是的问题）
cout << "dynamic_cast test" << endl;
//下面这个代码circle的指针指向一个circle，这种实体就是circle，是转不成shape的，
//c= new Circle("c");

//下面这个代码，基类指针指向了子类
base = new Circle("c 12");
c = dynamic_cast<Circle*>(base);
delete base;
delete c;
cout << "dynamic_cast over" << endl;
return 0;
}

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