指针指向类成员使用

代码：

#include<iostream>
using namespace std;

class Test
{
public:
	void func() { cout << "call Test::func" << endl; }
	static void static_func();
	int ma;

	static int mb; //不依赖对象
};
void Test::static_func() { cout << "Test::static_func " << endl; }
int Test::mb;
int main()
{
	Test t1;
	Test* t2 = new Test();
	//int a= 10; int *p =&a; *p = 30;
	//无法从"int Test::* 转换为 int *;
	int Test::* p = &Test::ma;
	//*p = 20;//错误
	t1.*p = 20;
	cout << "t1.ma = " << t1.ma << endl; //通过ma来看
	t2->*p = 30;
	cout << "t2-->ma = " << t2->ma << endl; //通过ma来看

	int* p1 = &Test::mb;
	*p1 = 40;
	cout << Test::mb << endl;

	//指向成员方法的指针
	//无法转换 “初始化”: 无法从“void (__cdecl Test::* )(void)”转换为“void (__cdecl *)(void)” 
	void(Test:: * func)() = &Test::func;
	(t1.*func)();
	(t2->*func)(); //普通成员函数依赖对象

	//定义一个函数指针指向类的静态成员函数
	void(*pfunc)() = &Test::static_func;
	(*pfunc)();
	delete t2;
	return 0;
}

总结：针对类成员普通的指针需要指定对象

2、深浅拷贝

#include<iostream>
#include<string>
using namespace std;

class People
{
public:
	People(const char* _name) : name(new char[strlen(_name) + 1])
	{
		strcpy_s(name, strlen(_name) + 1, _name);
	}

	People(const People& other) :name(new char[strlen(other.name) + 1]) //开辟控件赋值的是深拷贝
	{
		strcpy_s(name, strlen(other.name) + 1, other.name);
	}

	//深拷贝
	People& operator =(const People& other)
	{
		name = new char[strlen(other.name) + 1];
		strcpy_s(name, strlen(other.name) + 1, other.name);
	}
	~People()
	{
		delete[] name;
		cout << "析构函数" << typeid(*this).name() << endl;
	}

	void print()
	{
		cout << name << endl;
	}

private:
	char* name;
};

int main()
{
	People a("shabi");
	People b(a);
	People c = b;
	c.print();
	b.print();
	a.print();
	return 0;
}

效果如下：

3、构造和析构函数

#include<iostream>
using namespace std;

#include<time.h>
//构造函数和析构函数的讲解
class SeqStack
{
public:
	/*void init(int size = 10)
	{
		_stack = new int[size];
		_top = -1;
		_size = size;
	}*/
	SeqStack(int size = 10) //可以重载，多个参数
	{
		_stack = new int[size];
		_top = -1;
		_size = size;
	}

	/*void release()
	{
		delete[] _stack;
		_stack = nullptr;
	}*/

	~SeqStack()
	{
		delete[] _stack;
		_stack = nullptr;
		cout << "析构函数" << endl;
	
	}

	void push(int val)
	{
		if (full())
		{
			resize();
		}
		_stack[++_top] = val;

	}
	void pop()
	{
		if (empty())
		{
			return;
		}
		--_top;
	}
	int top()
	{
		return _stack[_top];
	}

	bool empty()
	{
		if (_top == -1)return true;
		return false;
	}

	bool full() { return _top == _size - 1; }
private:
	int* _stack;
	int _size;//存储顺序栈的元素
	int _top; //指向栈顶的位置

	void resize()
	{
		int* tmp = new int[_size * 2];
		for (int i = 0; i < _size; i++)
		{
			tmp[i] = _stack[i];
			//memset(tmp,_stack,sizeof(int)*_size);realloc 内存的拷贝
		}
		delete[] _stack;
		_stack = tmp;
		tmp = nullptr;
		_size *= 2;
	}
};

int main()
{
	SeqStack s;

	for (int i = 0; i < 15; i++)
	{
		s.push(rand() % 100);
	}
	while (!s.empty())
	{
		cout << s.top() << " ";
		s.pop();
	}
	//s.release();//释放成员变量占用的外部堆内存
	return 0;
}

效果如下：

4、构造函数的初始化列表

#include<iostream>
using namespace std;
#include<string>

/*
构造函数的初始化列表

*/

//日期类
class CDate
{
public:
	CDate(int y, int m, int d) :_year(y), _month(m), _day(d) //自定义之后不会再产生默认的构造函数了
	{

	}

	void show()
	{
		cout << "_year " << _year << endl;
		cout << " _month" << _month << endl;
		cout << "_day" << _day << endl;
	}
private:
	int _year;
	int _month;
	int _day;

};
class CGoods
{
public:
	CGoods(const char* n, int a, double p, int y, int m, int d) :_date(y, m, d) //初始化的列表功能
	{
		strcpy_s(_name, strlen(n) + 1, n);
		_amount = a;
		_price = p;
	}
	void show()
	{
		cout << "name : " << _name << endl;
		cout << "amount: " << _amount << endl;
		cout << "price: " << _price << endl;
	}
	CDate test()
	{
		return _date;
	}
private:

	char _name[20];
	int _amount;
	double _price; //初始化顺序的时候，先name按照先后哈
	/*
	Test(int data = 10):mb(data),ma(mb);
	private:
		int ma;
		int mb;先初始化ma然后是mb
	*/
	CDate _date; //成员对象 没有合适的默认构造函数 说明写了之后，默认的就没了
};

int main()
{
	CGoods c("张三", 12, 12, 1, 1, 1);
	c.show();
	c.test().show();
	return 0;
}

效果展示：

5、掌握类的各种成员方法以及区别

#include<iostream>
using namespace std;
#include<string>

/*
构造函数的初始化列表

*/

//日期类
class CDate
{
public:
	CDate(int y, int m, int d) :_year(y), _month(m), _day(d) //自定义之后不会再产生默认的构造函数了
	{

	}

	void show()
	{
		cout << "_year " << _year << endl;
		cout << " _month" << _month << endl;
		cout << "_day" << _day << endl;
	}
private:
	int _year;
	int _month;
	int _day;

};
class CGoods
{
public:
	CGoods(const char* n, int a, double p, int y, int m, int d) :_date(y, m, d) //初始化的列表功能
	{
		strcpy_s(_name, strlen(n) + 1, n);
		_amount = a;
		_price = p;
		goods_numbr++;
	}
	void show() const //常用方法
	{
		cout << "name : " << _name << endl;
		cout << "amount: " << _amount << endl;
		cout << "price: " << _price << endl;
	}
	CDate test()
	{
		return _date;
	}

	int get_number()
	{
		cout << "商品的总数量是: "<<goods_numbr << endl;
		//cout<<name;这种错的，不能访普通成员的变量
		return 1;
	}
private:

	char _name[20];
	int _amount;
	double _price; //初始化顺序的时候，先name按照先后哈
	/*
	Test(int data = 10):mb(data),ma(mb);
	private:
		int ma;
		int mb;先初始化ma然后是mb
	*/
	CDate _date; //成员对象 没有合适的默认构造函数 说明写了之后，默认的就没了

	//记录商品的成员变量数量
	static int goods_numbr; //不属于对象属于类级别
};
int CGoods::goods_numbr = 0;

int main()
{
	CGoods c("商品1", 12, 12, 1, 1, 1);
	CGoods c1("商品2", 12, 12, 1, 1, 1);
	CGoods c2("商品3", 12, 12, 1, 1, 1);
	CGoods c3("商品4", 12, 12, 1, 1, 1);
	c.show();
	c.test().show();
	c.get_number();
	//统计商品的总数量
	return 0;
}


/*
总结：
static静态成员方法
1、属于类的作用域
2、用类名作用域来调用方法
*/

6、类和对象、this指针

C++:OOP对象 OOP编程 this指针
C++：实体的抽象类型
四大特性： 抽象，封装，继承，多态
三种:公有私有以及保护 ，属性一般私有，提供公有的方法访问属性

7、实际运用

#include<iostream>
#include<string>
using namespace std;


//类和对象代码实践应用
class String
{
public:
	String(const char* str = nullptr)
	{
		if (str != nullptr)
		{
			m_data = new char[strlen(str) + 1];

			strcpy_s(this->m_data, strlen(str) + 1, str);
		}
		else
		{
			m_data = nullptr;
		}
	}
	String(const String& other)
	{
		if (this != &other)
		{
			m_data = new char[strlen(other.m_data) + 1];
			strcpy_s(m_data, strlen(other.m_data) + 1, other.m_data);

		}
		else
		{
			m_data = new char[1];
			*m_data = '\0';
		}
		
	}

	~String(void)//析构函数
	{
		delete[]m_data;
	}
	String& operator =(const String& other)
	{
		if (this == &other)
		{
			return *this;
		}
		delete[] m_data;
		m_data = new char[strlen(other.m_data) + 1];
		strcpy_s(m_data, strlen(other.m_data) + 1, other.m_data);
		return *this;
	}
private:
	char* m_data;

};

int main()
{
	String str1;
	String str2("hello");
	String str3(str2);
	String str4 = str3 = str2;//调用赋值重载函数
}

//循环队列 memcpy realloc 不太合适
#include<iostream>
#include<time.h>
using namespace std;

class Queue
{
public:
	Queue(int size = 5)
	{
		_queue = new int[size];
		_front = _rear = 0;
		_size = size;
	}
	//Queue(const Queue&) = delete;
	//Queue& operator=(const Queue&) = delete;
	Queue(const Queue& src)
	{
		_size = src._size;
		_front = src._front;
		_rear = src._rear;
		_queue = new int[_size];
		for (int i = _front; i != _rear; i++)
		{
			_queue[i] = src._queue[i];
		}
	}

	Queue& operator = (const Queue& src)
	{
		if (this == &src)return *this;
		_size = src._size;
		_front = src._front;
		_rear = src._rear;
		_queue = new int[_size];
		for (int i = _front; i != _rear; i++)
		{
			_queue[i] = src._queue[i];
		}
		return *this;
	}
	~Queue()
	{
		delete[] _queue;
		_queue = nullptr;
	}

	void push(int val) //入队操作
	{
		if (full())
		{
			resize();
		}
		_queue[_rear] = val;
		_rear = (_rear + 1) % _size;
	}
	void pop()
	{
		if (empty())
		{
			return;
		}
		_front = (_front + 1) % _size;
	}

	int front()
	{
		return _queue[_front];
	}
	bool full() { return (_rear + 1) % _size == _front; }
	bool empty() { return _front == _rear; }


private:
	int* _queue;
	int _front;
	int _rear;
	int _size;

	void resize()
	{
		int* ptmp = new int[2 * _size];
		int index = 0;
		for (int i = _front; i != _rear; i = (i + 1) % _size)
		{
			ptmp[index++] = _queue[i];
		}
		delete[]_queue;
		_queue = ptmp;
		_front = 0;
		_rear = index;
		_size *= 2;
	}
};

int main()
{
	Queue queue;

	for (int i = 0; i < 20; i++)
	{
		queue.push(rand() % 100);
	}
	Queue queue1 = queue;//删掉了拷贝构造就不行了
	while (!queue1.empty())
	{
		cout << queue1.front() << " ";
		queue1.pop();
	}
}