拾人牙慧，浅记一些C++的类

      这两天没事又翻了翻Primer，发现自己上岁数了，记单词能力开始下降，索引把一些简单的例子记下来，把一些肥肉剔除，剩一下骨头，方便今后Ctrl+F。

　　  在此感谢：

　　   http://ticktick.blog.51cto.com/823160/194307/

         http://www.cnblogs.com/gaojun/archive/2010/09/10/1823354.html

　　   http://www.cnblogs.com/uniqueliu/archive/2011/08/02/2125590.html

一、类的初始化--构造函数。

#include<iostream>
#include<memory>
#include<unistd.h>

using namespace std;

class Tree
{
public:
        int data;
        int data_arr[3];
        double hello;
        //无参数构造函数
        //编译系统对象分配内存空间，并自动调用该构造函数->由构造函数完成成员的初始化工作
        Tree(void)
        {
           hello=9.823;
           data=22;
        }
        //一般构造函数
        Tree(double a)
        {
           hello=a; 
        }
        //复杂构造函数
        Tree(const Tree &c)
        {
      hello=c.hello;
        }
        //等号运算符重载构造函数
        Tree &operator=(const Tree &rt)
        {
           if(this==&rt)
           {
                 return *this;
           }
           this->hello=rt.hello;
           this->data=rt.data;

           return *this;
        }

private:
        int price;
        int num;

};


int main()
{
  //一般构造
  Tree a(233.33); 
  cout<<a.hello<<endl;
  //复杂构造
  Tree b(a);
  cout<<b.hello<<endl;
  //等号运算构造
  Tree c=a;
  cout<<c.hello<<endl;
}

　　

二、深、浅拷贝--防止DELETE二次错误。

//深拷贝和浅拷贝
#include<iostream>
#include<memory>
#include<string.h>
#include<stdio.h>

using namespace std;


class Tree
{
public:
        Tree(char *pN)
        {
           m_pName = new char[strlen(pN) + 1];
           if(m_pName)
           {
                        strcpy(m_pName ,pN); 
           }
        }
    
        Tree(Tree &p)
        {
                m_pName=new char[strlen(p.m_pName)+ 1];
                if(m_pName)
                {
                        strcpy(m_pName ,p.m_pName);
                }
        }

        ~Tree()
        {
           delete m_pName;
        }
private:
        char *m_pName;
};

int main()
{
    Tree man("lujun");
        Tree woman(man);

}

　　

三、友元---我的世界你不懂，你的世界我能懂

#include<iostream>
#include<memory>
#include<string.h>
#include<stdio.h>

using namespace std;


class TV
{
public:
        friend class Control;
        TV():volume(20){}
        void Show(TV &t)const;
private:
    int volume;
};


class Control
{
public:
        bool VolumeUp(TV &t);
        bool VolumeDown(TV &t); 
        void Show(TV &t)const;
};

bool Control::VolumeUp(TV &t)
{
   t.volume++;
}

bool Control::VolumeDown(TV &t)
{
   t.volume--;
}

void Control::Show(TV&t)const
{
        cout<<"经遥控器调整的音量大小为："<<t.volume<<endl;
}

void TV::Show(TV&t)const
{
    cout<<"TV自身音量大小为："<<t.volume<<endl;
}



int main()
{
        Control c1;
        TV t1;
        c1.VolumeUp(t1);
        c1.Show(t1);
        c1.VolumeUp(t1);
        c1.Show(t1);
        c1.VolumeDown(t1);
        c1.Show(t1);
        t1.Show(t1);
}

四、基类、派生、虚、多态----剪不断理还乱

#include <iostream>

using namespace std;


//原始书籍类
class Quote
{
public:
        string isbn() const;
        virtual double net_price(int n) const;  //返回实际销售价格
        Quote(void)
        {
           price=9.987;
        }
protected:
        double price;
};



string Quote::isbn() const
{
   string aa="abcd,world";
   cout<<aa<<endl;
   return aa;
}

double Quote::net_price(int n) const
{
   cout<<n+20<<endl;
   return n+20;
}

//打折书籍类
class BulkQuote:public Quote
{
public:
        BulkQuote()=default;
        double net_price(int n) const ;   //返回改动后的价格+自动覆盖
};

double BulkQuote::net_price(int n) const
{
        cout<<n+10<<endl;
        cout<<"n_price="<<n*price<<endl;
        return n+10;
}

void PrintAll(const Quote &book);  //根据实际传的类类型，进行动态鉴别


int main()
{
        Quote Father,*f;
        BulkQuote Son,*s;


        Father.isbn();
        Father.net_price(100);
        cout<<endl;

        Son.isbn();
        Son.net_price(100);
        cout<<endl;

        PrintAll(Father);
        PrintAll(Son);

}

void PrintAll(const Quote &book)
{
    book.net_price(1000);
};

五、类模板、容器模板--真心方便

#include <iostream>
#include <vector>
#include <list>

using namespace std;

template<typename T1,typename T2>
class Tree
{
private:
        T1 I;
        T2 J;
public:
        Tree(T1 a,T2 b);
        void show();
};

template <typename T1,typename T2>
Tree<T1,T2>::Tree(T1 a,T2 b):I(a),J(b){}

template <typename T1,typename T2>
void Tree<T1,T2>::show()
{
        cout<<"I="<<I<<",J="<<J<<endl;
}

template <typename X>
void print(X v)
{
   typename X::iterator itor;
   for (itor = v.begin(); itor != v.end(); ++itor)
   {
          cout<<*itor<<endl;
   }
}



int main()
{
        Tree<int,int> t1(33,55);
        t1.show();
        Tree<int,string> t2(99,"wenzhang");
        t2.show();
        Tree<double,string> t3(3.414,"mayili");
        t3.show();
        vector<int> v1;
        v1.push_back(2);
        v1.push_back(33);
        v1.push_back(44);
        print(v1);
}

六、tuple类型--自己也能MongoDB

#include <iostream>
#include <tuple>
#include <vector>
#include <list>

using namespace std;

int main()
{
        tuple<string,vector<double>,int,list<int> > aa("头条",{1.1,3.4},42,{3,4,5,6,7,9});
    auto item=make_tuple("play",3,99.239);

        cout<<get<0>(item)<<endl; 
}