day-15

1. delete 和 new

2. 函数重载

3. 内联函数

4. 常量

5. 引用

常量引用

int x = 1;
const int& y = x;
x = 2;
cout << y << endl;

/*output
2
*/

函数引用

int& func2(int* pint)
{
	return *pint;
}

int a = 10, b;
b = func2(&a) * 5;
func2(&a) = 70;  //不能省略int&的&
cout << "a = " << a << ", b = " << b << endl;
/*output
a = 70, b = 50
*/

6. 对象指针

7. 拷贝构造函数

8. 类对象做参数类型的三种方式

9. 类对象数组初始化数据初始化

数组初始化

class example1
{
public:
    int val3;
};

class example
{
public:
    int val1;
    int val2;
    example1 exam;
};
//如果example发生值初始化，则定义在example中的exam成员变量发生值初始化。
//如果example发生默认初始化，则定义在example中的exam成员变量发生默认初始化。

example ex;                     //ex 值初始化

void printClass()
{
    example ex1;                //ex1 默认初始化                                     
    example exArr[2] = {};      //exArr[1],exArr[2] 值初始化

    cout << "ex.val1 = " << ex.val1 << endl;            //ex.val1值初始化 为0
    cout << "ex.val2 = " << ex.val2 << endl;            //ex.val2值初始化 为0
    cout << "ex.exam.val3 = " <<ex.exam.val3 << endl;   //ex.exam值初始化 ex.exam.val3值初始化 为0

    cout << "ex1.val1 = " << ex1.val1 << endl;          //ex1.val1 默认初始化 未定义值
    cout << "ex1.val2 = " << ex1.val2 << endl;          //ex1.val2 默认初始化 未定义值
    cout << "ex1.exam.val3 = " <<ex1.exam.val3 << endl; //ex1.exam 默认初始化 ex1.exam.val3 默认初始化 未定义值

    cout << "exArr[1].val1 = " << exArr[1].val1 << endl;    //exArr[1].val1值初始化 为0
    cout << "exArr[1].val2 = " << exArr[1].val2 << endl;    //exArr[1].val2值初始化 为0
    cout << "exArr1[].exam.val3 = " << exArr[1].exam.val3 << endl;  //exArr[1].exam值初始化 exArr[1].exam.val3值初始化 为0
}

10. 静态数据成员：只能在类外定义初始化，在类内声明。所有类对象都有同一个静态数据成员，这个静态数据成员都有同一个地址。不属于类对象，属于类

静态数据成员

class Counter
{
public:
	void setCount(int num)
	{
		count = num;
	}
	void showCount()
	{
		cout << "count = " << count << endl;
	}

private:
	static int count;
};

int Counter::count = 0;

int main()
{
	Counter c1, c2;
	c1.showCount();
	c2.showCount();
	c1.setCount(20);
	c1.showCount();
	c2.showCount();

	cout << endl;
	return 0;
}

/*output
count = 0
count = 0
count = 20
count = 20
*/