【C++】cast类型转换详解

一.知识点

static_cast静态转换, 适用于C中的隐式转换

reinterpret_cast强制解释转换, 适用于C中的指针或引用的强制类型转换

dynamic_cast可由父类指针转为子类指针, 且如果转换失败( 如传入为父类 或 传入为另一子类 )会抛出bad_cast–用来识别函数中形参传入的是哪一子类指针

const_cast将函数中形参传入的const解const, 但需要注意, 只有对于本身不是const的指针才有效, 因为本身const char*位于常量数据区, 访问权限仅可读. 且只能修改指针或引用, 因指针或引用可能指向对象占用空间大, 转换有意义, 而基本类型占用空间小, 如int, 直接申请新的int空间即可, 占用内存小不必转换

( 文字常量区见下 )

二.示例

static_reinterpret_cast.cpp

#include 
#include 
#include 
#include 
using namespace std;

class Animal
{
public:
	virtual void cry()
	{
		cout << "动物叫" << endl;
	}

};
class Dog:public Animal
{
public:
	void cry()
	{
		cout << "狗狗叫!" << endl;
	}
};
class Cat:public Animal
{
public:
	void cry()
	{
		cout << "猫猫叫!" << endl;
	}
};

void demo(Animal* animal)
{
	Dog* dog = dynamic_cast<Dog*>(animal);
	if (dog)
	{
		dog->cry();
	}
}
int main() {
	
	char c;
	int i = c;
	int ii = (int)c;
	int iii = static_cast<int>(c);
	//int iiii = reinterpret_cast(c);×

	float f;
	int iiiii = f;
	int iiiiii = (int)f;
	int iiiiiii = static_cast<int>(f);
	//int iiiiiiii = reinterpret_cast(f);×

	int* p = reinterpret_cast<int*>(0x66666);
	//int* pp=static_cast(0x66666);×

	Dog* dog;
	Animal* animal = reinterpret_cast<Animal*>(dog);
	Cat* cat = reinterpret_cast<Cat*>(animal);// 风险:子类转换错误!dog->animal->cat

	return 0;
}

dynamic_cast.cpp

#include 
#include 
#include 
#include 
using namespace std;

class Animal
{
public:
	virtual void cry()
	{
		cout << "动物叫" << endl;
	}

};
class Dog:public Animal
{
public:
	void cry()
	{
		cout << "狗狗叫!" << endl;
	}
};
class Cat:public Animal
{
public:
	void cry()
	{
		cout << "猫猫叫!" << endl;
	}
};

void demo(Animal* animal)
{
	Dog* dog = dynamic_cast<Dog*>(animal);
	if (dog)
	{
		dog->cry();
	}
}
int main() {
	
	Animal a;
	demo(&a);

	return 0;
}

const_cast.cpp

#include 
using namespace std;

void deConst(const char* str)
{
	char* p = const_cast<char*>(str);
	p[0] = 'A';

	const_cast<char*>(str)[1] = 'Z';
}
int main() {
	
	char cStr[] = "12345";
	const char conStr[] = "12345";
	deConst(cStr);
	deConst(conStr);
	cout << cStr << endl;// AZ345
	cout << conStr << endl;// AZ345

	const char* p_c = "123";
	//deConst(p_c);×

	return 0;
}