《Essential C++》系列笔记之第四章(基于对象的编程风格)之第三节(何谓mutable(可变)和const(不变))

代码实践

#include 
using namespace std;
#include 

class Teacher
{
public:
	Teacher(int age, string name, int tel_number) 
		: _age(age), _name(name), _tel_number(tel_number)
	{}

	void display_age() const
	{
		cout << "const" << endl;
		/*_age = 19;*/ //错误,因为这是const修饰的member function 不可改变data member(准确的说是class object)!
		cout << _age << endl;
	}

	//void display_age()  //注意  这里说明const可以发送函数重载
	//{
	//	cout << "no const" << endl;
	//	cout << _age << endl;
	//}

	void display_tel_number() const
	{
		cout << _tel_number << endl;
	}

	void revise_tel_number(int number) const
		/*:_tel_number(number)*/ //错误,因此有了const就在函数体内操作吧
	{
		//修改电话号码
		_tel_number = number; //可以修改,因为是_tel_number是multable
	}


private:
    int _age;
	string _name;
	//int _tel_number;
	mutable int _tel_number;
};

int main()
{
	const Teacher teacher(18, "teacher", 12345); 
	teacher.display_age();  //如果teacher使用了const 那么就必须存在const版本的 如果没有const 优先选择无const版本,在这里最好加上const
	teacher.display_tel_number();

	teacher.revise_tel_number(520);
	teacher.display_tel_number();

	system("pause");
	return 0;
}

今天是20200317 今天重装了系统,有得(才怪)有失(很多)啊