C++ 补充 & C++ 11 - explicit 关键字

explicit 关键字

explicit /ɪkˈsplɪsɪt/ 明确的；清楚的；直率的；详述的

作用是表明该构造函数是显示的, 而非隐式的.不能进行隐式转换! 跟它相对应的另一个关键字是implicit, 意思是隐藏的,类构造函数默认情况下即声明为implicit(隐式).

demo1 代码:

#include 
#include 

using namespace std;

class student
{
public:
	student(int _age)
	{
		this->age = _age;
		cout << "arg=" << age << endl;
	}

	student(int _age, const string _name)
	{
		this->age = _age;
		this->name = _name;
		cout << "age=" << age << "; name=" << name << endl;
	}

	~student()
	{

	}

	int getAge()
	{
		return age;
	}

	string getName()
	{
		return name;
	}

private:
	int age;
	string name;

};


int main(void)
{
	student xiaoM(18); /* 显示构造 */
	student xiaoW = 18; /* 隐式构造 */

	student xiaoHua(19, "小花"); /* 显示构造 */
	student xiaoMei = { 18, "小美" }; /* 隐式构造 初始化参数列表, C++11 前编译不能通过, C++11 新增特性 */

	system("pause");
	return 0;
}

demo2 代码

#include 
#include 

using namespace std;

class student
{
public:
	explicit student(int _age)
	{
		this->age = _age;
		cout << "arg=" << age << endl;
	}

	explicit student(int _age, const string _name)
	{
		this->age = _age;
		this->name = _name;
		cout << "age=" << age << "; name=" << name << endl;
	}

	~student()
	{

	}

	int getAge()
	{
		return age;
	}

	string getName()
	{
		return name;
	}

private:
	int age;
	string name;

};


int main(void)
{
	student xiaoM(18); /* 显示构造 */
	student xiaoW = 18; /* 隐式构造 */

	student xiaoHua(19, "小花"); /* 显示构造 */
	student xiaoMei = { 18, "小美" }; /* 隐式构造 初始化参数列表, C++11 前编译不能通过, C++11 新增特性 */

	system("pause");
	return 0;
}

这样的话隐式就会报错, 显示就会没问题.

结语:

时间: 2020-06-30