1 静态类型转换和强制类型转换

1 static_cast reinterpret_cast

#include<iostream>
using namespace std;

void main() {
	double dpi = 3.1415926;
	int num1 = (int)dpi;	//C类型转换
	int num2 = static_cast<int>(dpi);	//静态类型转换	编译时C++编译器会做类型检查
	int num3 = dpi;	//C语言中隐式类型转换均可使用static_cast<>()

	// char * ===> int *
	char* p1 = (char *)"hello...itcast";
	int* p2 = NULL;
	// p2 = static_cast<int*>p1;	// 使用static_cast<>()编译器编译时会做类型检查 若有错误提示错误

	p2 = reinterpret_cast<int*>(p1);

	cout << "p1:" << p1 << endl;
	cout << "p2:" << p2 << endl;

	// 通过 static_cast<>() 和 reinterpret_cast<>() 实现C语言强制类型转换
}

结果

p1:hello...itcast
p2:006D9B30

2 dynamic_cast

动态类型转换，安全的基类和子类之间转换；运行时类型检查

#include<iostream>
using namespace std;

class Tree {};

class Animal {
public:
	virtual void cry() = 0;
};

class Dog :public Animal{
public:
	void cry() {
		cout << "wangwang" << endl;
	}
	void athome() {
		cout << "at home" << endl;
	}
};

class Cat :public Animal {
public:
	void cry() {
		cout << "miaomiao" << endl;
	}
	void catch_mouse() {
		cout << "catch_mouse" << endl;
	}
};

void objplay(Animal *base) {
	base->cry();	//	1继承 2 虚函数重写 3 父类指针 指向子类对象==>多态
	// 能识别子类对象
	
	// dynamic_cast 运行时类型识别 RIIT
	Dog* pdog = dynamic_cast<Dog*>(base);
	if (pdog != NULL) {
		pdog->athome();	//特定类任务
	}

	Cat* pcat = dynamic_cast<Cat*>(base);	//父类对象 ===> 子类对象 向下转型
	if (pcat != NULL) {
		pcat->catch_mouse();//特定类任务
	}

}

void main() {
	Dog d1;
	Cat c1;

	Animal* pBase = NULL;
	pBase = &d1;

	pBase = static_cast<Animal*>(&d1);

	// 强制类型转换
	pBase = reinterpret_cast<Animal*>(&d1);


	{
		Tree t1;
		// pBase = static_cast<Animal*>(&t1);	//C++编译器会做类型检查 报错

		// 强制类型转换
		pBase = reinterpret_cast<Animal*>(&t1);// 重新解释、强制类型转换
	}
	//
	
	objplay(&d1);
	objplay(&c1);
}

结果

wangwang
at home
miaomiao
catch_mouse

3 const_cast

去除变量只读属性

#include<iostream>
using namespace std;

// const char *p 让p指向的内存空间变成只读属性
void printBuf(const char* p) {
	//p[0] = 'z';
	char* p1 = NULL;

	//const char*==>char * 把只读属性去掉
	p1 = const_cast<char*>(p);
	p1[0] = 'Z';
	cout << p << endl;
}

void main() {
	char buf[] = "abdfefadf";

	// char* myp = "asdfasdasfasf";

	// 要确保p指向的内存空间确实可以修改，不然产生意想不到的后果

	// printBuf(myp);
	printBuf(buf);
}