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();}
}
