本文主要探讨C类的相关知识。构造和析构函数构造函数(可多个)对象产生时调用初始化class属性、分配class内部需要的动态内存析构函数一个对对象消亡时调用回收分配动态内存C提供默认构造和析构,构造函数可重载,析构函数不需重载构造和析构函数不需要返回值类型,构造函数可带参或不带参,析构函数不带参无其他构造函数时默认构造函数可省略,有构造函数时默认构造函数不能省class声明时可给构造函数形参赋默认值,调用时不传参则使用默认值,调用不能有重载歧义所有参数都带默认值构造函数,可以表示所有构造函数拷贝构造函数用对象来初始化对象,函数不需重载浅拷贝:普通成员变量初始化的拷贝构造函数(默认提供),有动态内存分配时出错深拷贝:浅拷贝无法拷贝对象的成员指针已分配的内存空间,深拷贝可以拷贝显式提供copy constructor为深拷贝,拷贝构造函数用原来的析构函数权限public类内、类外可访问,子类可访问父类公共成员protected类内可访问,类外不可,子类可访问父类保护成员private类内可访问,类外不可,子类不可访问父类私有成员默认是private继承,struct是public继承继承中父类所有权限继承给子类public继承父类成员在子类中保持原有访问权限private继承父类成员在子类中变为private权限protected继承父类public变protected,protected为protected,private为privatestruct和classC不支持成员函数,C支持C不支持static成员,C中支持C默认public,C默认public,c可指定public/private/protected权限C不支持继承(通过包含结构体指针实现),C支持且struct和class可互相继承C中struct和class:struct默认public,class默认private,struct和class交叉继承权限取决子类派生类和基类派生类不继承基类构造和析构函数,只继承成员变量和成员方法,派生类有自己构造和析构派生类构造函数执行前,先调用基类构造函数,再调用自己构造函数派生类先执行自己析构函数,再执行基类析构函数派生类覆盖基类同名成员(重定义),父类的同名成员存在且被隐藏,可通过全域路径调用被隐藏的方法,可添加派生类独有成员派生类是基类的超集,基类对象放大成派生类可能出错,派生类赋值给基类可正常使用(类似char和int的兼容性)多继承二义性和多态C多继承A和B,A和B有同名成员、菱形继承(B1:A, B2:A, C:B1,B2)造成二义性全域路径调用方法,重定义子类方法,重写虚函数解决二义性基类方法声明为virtual,派生类重写同名方以实现多态重载函数名相同参数列表不同,重定义子类实现父类同名方法后把父类方法隐藏重写子类去实现父类同名virtual方法实现多态特性虚函数抽象类:有纯虚函数的类,抽象类只能为基类派生新类,不可实例化对象派生类必须实现基类纯虚函数才能用于实例化对象,否则派生类仍为基类接口类中所有成员函数是public且是纯虚函数无虚构造函数,包含虚函数的类只能作为基类派生新类,无法实例化对象,构造函数是在实例化的时候被调用的,故无虚构造函数抽象基类(接口)指针指向派生类(new派生类对象person *p new man; delete p;),抽象基类(接口)析构函数需要为虚,才可删除指针时能正确调用派生类析构函数,否则不会调用派生类析构函数抽象基类(接口)指针指向派生类(定义好的派生类man m;person *p m;),抽象基类(接口)析构函数是否为虚,都能正常调用派生类析构函数,一般抽象基类(接口)的析构函数都定义为虚运算符重载运算符重载是重定义对象运算符对应函数赋值运算符默认提供,重载有指针成员时涉及浅拷贝和深拷贝a对应Type operator(void);a,对应Type operator(int x);不可重载运算符: .,.*, -*,sizeof,?,:,#静态成员静态成员属于class本身,不属于对象静态成员变量在类的多个对象中均可访问,且是同一个静态成员变量和方法可以用对象调用,也可不产生对象的本身调用静态数据成员不在类中初始化,类只定义模版静态数据成员不在类构造函数中初始化,构造函数用于构建对象时初始化对象成员静态数据成员值默认0,遵循publicprivateprotected访问准则静态方法只访问静态成员变量和方法,不能直接访问非静态,需要通过函数传参访问非静态静态成员变量可用于统计对象数静态类:内部全是静态成员,不能被实例化,不包括构造函数,不能实现接口(不能被继承),不能有实例成员静态类成员不能有protected或protected internal访问保护修饰符友元函数友元函数不是本类成员函数,是外部函数友元函数在private或protected或public都可可以通过类来访问友元函数,不能直接通过友元函数访问类(常用传参访问)友元函数破坏了封装机制,实现类之间数据共享时减少系统开销,提高效率运算符重载可用友元函数除,-,[],()类间的数据共享可用友元函数demo1类成员权限构造和析构函数深拷贝和浅拷贝目录run.sh#!/bin/bash if [ -f ./Makefile ] then make clean fi cmake . make echo --------------------------------- ./proCMakeLists.txtCMAKE_MINIMUM_REQUIRED(VERSION 2.20) #最低版本要求 SET(CMAKE_CXX_COMPILER g) #设置g编译器 PROJECT(CLASS) #设置工程名 MESSAGE(STATUS class test) #打印消息 ADD_EXECUTABLE(pro main.cpp person.cpp) #生成可执行文件person.hpp#ifndef __PERSON_HPP__ #define __PERSON_HPP__ #include iostream using namespace std; namespace People { class Person { public: string name; int age; string sex; string description; int *luck_num; Person(); Person(string name xxx,int age 0,string sex none,string description none); Person(const Person p); ~Person(); void set_info(string name,int age,string sex,string description); void print_info(); void set_income(int income); int get_income(); void set_savings_account(int savings_account); int get_savings_account(); private: int income; int savings_account; }; } #endifperson.cpp#include person.hpp #include iostream using namespace std; void People::Person::set_info(string name,int age,string sex,string description) { this-name name; this-age age; this-sex sex; this-description description; } void People::Person::print_info() { cout name : this-name endl; cout age : this-age endl; cout sex : this-sex endl; cout description : this-description endl; cout income get_income() endl; cout savings_account get_savings_account() endl; cout luck_num : this-luck_num[0] this-luck_num[1] endl; } void People::Person::set_income(int income) { this-income income; } int People::Person::get_income() { return this-income; } void People::Person::set_savings_account(int savings_account) { this-savings_account savings_account; } int People::Person::get_savings_account() { return this-savings_account; } People::Person::Person() { cout default constructor function endl; } People::Person::Person(string name,int age,string sex,string description):name(name),age(age),sex(sex),description(description) { this-luck_num new int[2]; cout user define constructor function endl; } People::Person::~Person() { delete [] this-luck_num; cout user define destructor function endl; } People::Person::Person(const Person p):name(p.name),age(p.age),sex(p.sex),description(p.description) { luck_num new int(*p.luck_num); cout user define deep copy constructor function endl; }main.cpp#include iostream #include person.hpp using namespace std; using namespace People; int main() { Person p1(xiaoming,23,male,high); p1.set_income(50); p1.set_savings_account(100); p1.luck_num[0] 2; p1.luck_num[1] 7; p1.print_info(); Person p2(p1); p2.set_income(20); p2.set_savings_account(10); p2.luck_num[0] 36; p2.luck_num[1] 72; p2.print_info(); Person p3 p2; p3.set_income(10); p3.set_savings_account(40); p3.luck_num[0] 5; p3.luck_num[1] 8; p3.print_info(); return 0; }结果示例demo2继承和多态,虚函数抽象类接口目录run.sh#!/bin/bash if [ -f ./Makefile ] then make clean fi cmake . make echo --------------------------------- ./procheck_mem.shvalgrind --toolmemcheck --leak-checkfull --show-reachableyes --trace-childrenyes -s ./proCMakeLists.txtCMAKE_MINIMUM_REQUIRED(VERSION 2.20) #最低版本要求 SET(CMAKE_CXX_COMPILER g-11) #设置g编译器 set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} -g) #添加编译选项 PROJECT(CLASS) #设置工程名 MESSAGE(STATUS class test) #打印消息 ADD_EXECUTABLE(pro main.cpp person.cpp man.cpp) #生成可执行文件person.hpp#ifndef __PERSON_HPP__ #define __PERSON_HPP__ #include iostream using namespace std; namespace People { class Person { public: string name; int age; void print_info(); Person(); Person(string name,int age); ~Person(); private: int income; protected: }; class person { public: string name; virtual void play() 0; virtual ~person(); }; class machine { public: virtual void introduce() 0; virtual ~machine(); }; } #endifperson.cpp#include person.hpp #include iostream using namespace std; void People::Person::print_info() { cout name : this-name endl; cout age : this-age endl; } People::Person::Person() { cout Person constructor endl; } People::Person::Person(string name,int age):name(name),age(age) { cout user define Person constructor endl; } People::Person::~Person() { cout Person destructor endl; } People::person::~person() { cout user define person desturctor endl; } People::machine::~machine() { cout machine virtual function endl; }man.hpp#ifndef __MAN_HPP__ #define __MAN_HPP__ #include person.hpp class Man:public People::Person { public: string description; void do_job(); void print_info(); Man(); Man(string name,int age,string description); ~Man(); private: protected: }; class man:private People::Person { public: using Person::name; using Person::age; using Person::print_info; }; class gamer:public People::person { public: void play(); gamer(); ~gamer(); }; class sportsman:public People::person { public: void play(); sportsman(); ~sportsman(); }; class robot:public People::machine { public: void introduce(); robot(); ~robot(); }; #endifman.cpp#include man.hpp #include iostream using namespace std; void Man::do_job() { cout this-name working endl; } void Man::print_info() { cout name : this-name endl; cout age : this-age endl; cout description : this-description endl; } void gamer::play() { cout this-name playing game endl; } gamer::gamer() { cout user define gamer consturctor function endl; } gamer::~gamer() { cout user define gamer desturctor function endl; } sportsman::sportsman() { cout user define sportsman consturctor function endl; } sportsman::~sportsman() { cout user define sportsman desturctor function endl; } void sportsman::play() { cout this-name playing ping-pong endl; } void robot::introduce() { cout i am robot endl; } robot::robot() { cout robot consturctor function endl; } robot::~robot() { cout robot desturctor function endl; } Man::Man() { cout man constructor endl; } Man::Man(string name xxx,int age 0,string description xxx):Person(name,age),description(description) { cout user define man constructor endl; } Man::~Man() { cout man destructor endl; }main.cpp#include person.hpp #include man.hpp using namespace People; using namespace std; int main() { Man m1; //父类构造-子类构造-子类析构-父类析构 Man m2(xiaoming,23,height); m2.print_info(); m2.do_job(); m2.Person::print_info(); //全域路径访问隐藏父类方法 Person p1 m2; //子类初始化父类 p1.print_info(); man m3; m3.name xiaohua; m3.age 27; m3.print_info(); //using放开保护继承(class A :private/protected B) //需要保证抽象基类的析构函数为虚才能正常调用派生类析构函数 person *p new gamer; p-name gamer; p-play(); delete p; //抽象基类的析构函数是否为虚都能调用派生类析构函数 sportsman s; s.name sportsman; person *t s; t-play(); //接口和抽象基类的析构函数一般定义为虚 robot r; r.introduce(); return 0; }结果示例demo4:运算符重载目录run.sh#!/bin/bash if [ -f ./Makefile ] then make clean fi cmake . make echo --------------------------------- ./procheck_mem.shvalgrind --toolmemcheck --leak-checkfull --show-reachableyes --trace-childrenyes -s ./proclean.sh#!/bin/bash rm -rf CMakeFiles pro Makefile CMakeCache.txt cmake_install.cmakeCMakeLists.txtCMAKE_MINIMUM_REQUIRED(VERSION 2.20) #最低版本要求 SET(CMAKE_CXX_COMPILER g-11) #设置g编译器 set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} -g) #添加编译选项 PROJECT(CLASS) #设置工程名 MESSAGE(STATUS class test) #打印消息 ADD_EXECUTABLE(pro main.cpp) #生成可执行文件main.cpp#include iostream using namespace std; class coordinate { public: int *px; int *py; coordinate(); coordinate(const coordinate cd); coordinate(int x,int y); ~coordinate(); void print_coordinate(); coordinate operator(const coordinate other); coordinate operator(const coordinate other); coordinate operator(int x); //i coordinate operator(void); //i bool operator(const coordinate other); friend void operator(coordinate a,const coordinate b); //友元函数只能传参方式调用类成员 }; coordinate::coordinate() { this-px new int(0); this-py new int(0); } coordinate::coordinate(int x,int y) { this-px new int(x); this-py new int(y); } coordinate::coordinate(const coordinate cd) { cout copy endl; this-px new int(*(cd.px)); this-py new int(*(cd.py)); } coordinate::~coordinate() { delete this-px; delete this-py; } void coordinate::print_coordinate() { cout ( *(this-px) , *(this-py) ) endl; return; } coordinate coordinate::operator(const coordinate other) { cout endl; coordinate tmp; *(tmp.px) *(this-px) *(other.px); *(tmp.py) *(this-py) *(other.py); return tmp; } coordinate coordinate::operator(const coordinate other) { cout endl; if(this ! other) { *(this-px) *(other.px); *(this-py) *(other.py); } return *this; } coordinate coordinate::operator(void) { *(this-px) 1; *(this-py) 1; return *this; } coordinate coordinate::operator(int x) { coordinate tmp; *(tmp.px) *(this-px); *(tmp.py) *(this-py); *(this-px) 1; *(this-py) 1; return tmp; } void operator(coordinate a,const coordinate b) { *(a.px) *(b.px); *(a.py) *(b.py); return; } bool coordinate::operator(const coordinate other) { if(*(this-px) *(other.px) *(this-py) *(other.py)) return true; return false; } int main() { coordinate c1(1,1); coordinate c2(2,2); cout ------------3 endl; coordinate c3; c3 c1 c2; //先定义再赋值时,先调用加法,在调用自定义,在调用自定义拷贝(深浅拷贝均相同,浅拷贝时若为定义和拷贝,则调用默认) c3.print_coordinate(); cout ------------4 endl; coordinate c4 c1 c2; //只调用(深浅拷贝均相同) c4.print_coordinate(); cout ------------5 endl; coordinate c5 c1; //调用自定义拷贝(浅拷贝调用默认) c5.print_coordinate(); cout ------------6 endl; coordinate c6(c1); //调用自定义拷贝(浅拷贝调用默认) c6.print_coordinate(); cout tmp------------7 endl; coordinate tmp; coordinate c7; tmp c7; tmp.print_coordinate(); cout tmp------------8 endl; coordinate c8; tmp c8; tmp.print_coordinate(); cout ------------9 endl; coordinate c9(1,1); operator(c9,c9); c9.print_coordinate(); cout ------------10 endl; coordinate c10(1,1); bool res (c10 c1); cout boolalpha res endl; return 0; }结果示例demo5:类静态成员目录run.sh#!/bin/bash if [ -f ./Makefile ] then make clean fi cmake . make echo --------------------------------- ./proclean.sh#!/bin/bash rm -rf CMakeFiles pro Makefile CMakeCache.txt cmake_install.cmakecheck_mem.shvalgrind --toolmemcheck --leak-checkfull --show-reachableyes --trace-childrenyes -s ./proCMakeLists.txtCMAKE_MINIMUM_REQUIRED(VERSION 2.20) #最低版本要求 SET(CMAKE_CXX_COMPILER g-11) #设置g编译器 set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} -g) #添加编译选项 PROJECT(CLASS) #设置工程名 MESSAGE(STATUS class test) #打印消息 ADD_EXECUTABLE(pro main.cpp) #生成可执行文件main.cpp#include iostream using namespace std; class Person { public: string name; Person(); Person(string name); static int objetcion_num; static void print_obj_num(); static void print_name(string name); //静态方法传参访问非静态成员 }; //静态类 class constant { public: static int week_day_num; //一周的天数 static int earth_radius; //地球半径 static void print_info(); }; int constant::week_day_num 7; int constant::earth_radius 6371; void constant::print_info() { cout days of the week : constant::week_day_num endl; cout radius of the earth : constant::earth_radius endl; } int Person::objetcion_num 0; //int objetcion_num; //类中静态成员的访问方式 Person::Person() { objetcion_num; } Person::Person(string name) { this-name name; this-objetcion_num; } void Person::print_obj_num() { cout obj_num : Person::objetcion_num endl; } void Person::print_name(string name) { cout person name : name endl; } int main() { //类外静态成员的访问方式 Person p1; cout obj_num : p1.objetcion_num endl; Person p2(xaioming); cout obj_num : Person::objetcion_num endl; Person p3(xaiohua); p3.print_obj_num(); constant::print_info(); return 0; }结果示例demo6:友元函数友元类目录run.sh#!/bin/bash if [ -f ./Makefile ] then make clean fi cmake . make echo --------------------------------- ./procheck_mem.shvalgrind --toolmemcheck --leak-checkfull --show-reachableyes --trace-childrenyes -s ./proclean.sh#!/bin/bash rm -rf CMakeFiles pro Makefile CMakeCache.txt cmake_install.cmakeCMakeLists.txtCMAKE_MINIMUM_REQUIRED(VERSION 2.20) #最低版本要求 SET(CMAKE_CXX_COMPILER g-11) #设置g编译器 set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} -g) #添加编译选项 PROJECT(CLASS) #设置工程名 MESSAGE(STATUS class test) #打印消息 ADD_EXECUTABLE(pro main.cpp) #生成可执行文件main.cpp#include iostream using namespace std; //前置申明解决友元类未定义 class Father; class Son; class Father { public: string name; int age; Father(); Father(string name,int age); void print_name(string name); friend class Son; }; class Son { public: string name; int age; Son(); Son(string name,int age); void print_age(int age); friend class Father; }; Father::Father(string name,int age) { this-name name; this-age age; } void Father::print_name(string name) { cout name endl; } Son::Son(string name,int age) { this-name name; this-age age; } void Son::print_age(int age) { cout age endl; } int main() { Father f(xiaoming,40); Son s(xiaohua,20); f.print_name(s.name); s.print_age(f.age); return 0; }结果示例