c++primer读书笔记（6）

第十章的总结：
1.如果可以通过初始化，也可以通过赋值来设置对象的值，应采取初始化，通常效率会更高。
2.在函数声明后面加上const，可以确保不能在函数内更改属性值。
3.用户自己定义的数据类型，包含了数据的封装和函数
4.数据是私有的，方法是共用的。
5.构造函数在创建对象或者显式调用构造函数的时候调用，析构函数在对象过期被注销的时候调用。
代码练习：
6.没有参数或者所有的参数都有默认值的构造函数就是默认构造函数，不需要显式调用。可以声明对象而不初始化它，还可以声明数组。
7.this就是指向类对象自身的指针，在对象内可以使用，*this就是类对象的地址。
详细内容见

//stock00.h#ifndef _STOCK00_H_#define _STOCK00_H_#include <iostream>#include <string>using namespace std;class Stock{public:    Stock();    ~Stock();    Stock(const string & co, long n, double pr);    void buy(long num, double price);    void sell(long num, double price);    void update(double price);    void show() const;    const Stock & topval(const Stock & s) const;private:    string company;    long shares;    double share_val;    double total_val;    void set_tot() { total_val = shares * share_val; }};#endif//stock00.cpp#include <iostream>#include "stock00.h"#include<string>using namespace std;Stock::Stock(){    company = "no name";    shares = 0;    share_val = 0.0;    total_val = 0.0;}Stock::~Stock(){    cout << "by by" << endl;}Stock::Stock(const string & co,long n,double pr){    company = co;    if (n < 0)    {        cout << "Number of shares can't be negative;"            << company << "shares set to 0.\n";        shares = 0;    }    else    {        shares = n;    }    share_val = pr;    set_tot();}void Stock::buy(long num, double price){    if (num < 0)    {        cout << "Number of shares puchased can't be negative. "            << "transaction is aborted.\n";    }    else    {        shares += num;        share_val = price;        set_tot();    }}void Stock::sell(long num, double price){    if (num < 0)    {        cout << "Number of shares sold can't be negative. "            << "transaction is aborted.\n";    }    else if (num > shares)    {        cout << "You can't sell more than you have! "            << "Transaction is aborted.\n";    }    else    {        shares -= num;        share_val = price;        set_tot();    }}void Stock::update(double price){    share_val = price;    set_tot();}const Stock & Stock::topval(const Stock & s) const{    if (s.total_val > total_val)    {        return s;    }    else    {        return *this;    }}void Stock::show() const{    cout.setf(ios_base::fixed, ios_base::floatfield);    cout.precision(3);    cout << "Company: " << company        << " Shares: " << shares << endl;    cout << " Share Price: $ " << share_val        << " Total Worth: $ " << total_val << endl;}//main.cppconst int STKS = 4;int main(){    Stock stocks[STKS] =    {        Stock("NamoSmart",12,20.0),        Stock("Boffo Objects",200,2.0),        Stock("Monolthic",130,3.25),        Stock("Fleep Enterprises",60,6.5)    };    cout << "Stock holdings:" << endl;    int st;    for (st = 0;  st < STKS; st++)    {        stocks[st].show();    }    const Stock *top = &stocks[0];    for (st = 1; st < STKS; st++)    {        top = &top->topval(stocks[st]);    }    cout << "\nMost valuable valuable holding:\n";    top->show();    return 0;}

代码2：

#ifndef _TEST_H_#define _TEST_H_    class Test{public:    Test();    Test(const char *name);    Test(const Test & other);    Test & operator=(const Test & other);    ~Test();    void show();private:    char *name_;};#endif//test.cpp#include "Test.h"#include <iostream>#pragma warning(disable:4996)using namespace std;Test::Test(){}Test::Test(const char *name){    cout << "Test 1" << endl;    int len = strlen(name);    name_ = new char(len);    memset(name_, 0, len);    strcpy(name_, name);}Test::Test(const Test & other){    cout << "Test 2" << endl;    int len = strlen(other.name_) + 1;    name_ = new char(len);    memset(name_, 0, len);    strcpy(name_, other.name_);}Test::~Test(){    //delete name_;    cout << "delete name_ " << endl;}Test & Test::operator=(const Test & other){    cout << "Test = operator" << endl;    if (this == &other)    {        return *this;    }    int len = strlen(other.name_) + 1;    name_ = new char(len);    memset(name_, 0, len);    strcpy(name_, other.name_);    return *this;}void Test::show(){    cout << "Name: " << name_ << endl;}//main.cpp#include "Test.h"#include <iostream>using namespace std;int main(){    //Test p("wang");    Test p1;    p1 = "hello";    p1.show();    return 0;}

代码码3 实现stack的类

#ifndef _STACK_H_#define _STACK_H_typedef unsigned long Item;class Stack{public:    Stack();    bool isempty() const;    bool isfull() const;    bool push(const Item & item);    bool pop(Item & item);private:    enum{MAX = 10};    Item items[MAX];    int top;};#endif#include "Stack.h"#include <iostream>using namespace std;Stack::Stack(){    top = -1;}bool Stack::isempty() const{    return top == -1;}bool Stack::isfull() const{    return top == MAX - 1;}bool Stack::push(const Item & item){    if(isfull() == true)    {        cout <<"stack is full!" << endl;        return false;    }    top++;    items[top] = item;    return true;}bool Stack::pop(Item & item){    if(isempty() == true)    {        cout <<" stack is empty" << endl;        return false;    }    item =items[top--];    return true;}

//main.cpp

include “Stack.h”

include

include

using namespace std;

int main()
{
Stack st;
char ch;
unsigned long po;
cout <<”Please enter A to add a purchase order” << endl;
cout <<”P to process a PO,or Q to quit” << endl;

while(cin >> ch && toupper(ch) != 'Q'){    while(cin.get() != '\n')    {        continue;    }    if(!isalpha(ch))    {        cout << '\a';        continue;    }    switch(ch)    {        case 'A':        case 'a':        {            cout << "Entera PO number to add: ";            cin >> po;            st.push(po);            break;        }        case 'P':        case 'p':        {            if(st.pop(po) == true)            {                cout << "PO #" << po << "popped " << endl;            }            break;        }    }    cout << "Please enterA to add purchase order\n"        << "P to process a PO, or Q to quit." << endl;}cout << "Bye" << endl;return 0;

}