C++基础复习

C++

引用

int add（int &b） { b=b+1; return b; } int main() { int a=99; printf("%d\n",add(a)); }

构造函数

#include<iostream> using namespace std; class Person{ private: char *name; int age; char *work; public: Person(){cout<<"Person()"<<endl;} Person(char *name){ cout<<"Person(char *name)"<<endl; this->name=name; } Person(char *name,int age,char *work="none"){ cout<<"Person(char *name,int age)"<<endl; this->name=name; this->age=age; this->work=work; } void printfInfo(void) { cout<<"name="<<name<<" age="<<age<<" work="<<work<<endl; } }; int main() { Person Per("chenmiaohong",16); Person Per2;//调用无参数构造函数 Person Per3();//定义了一个函数Per3(); Person *per4=new Person;//调用无参数构造函数，创建对象的简写，与下面的写法相同 Person *per5=new Person();//调用无参数构造函数 Person *per6=new Person[2]; Person *per7=new Person("ls",18,"stu"); Person *per8=new Person("ww",16); Per.printfInfo(); per7->printfInfo(); per8->printfInfo(); delete per4; delete per5; delete []per6; delete per7; delete per8; return 0; }

析构函数

#include<iostream> #include<string.h> using namespace std; class Person{ private: char *name; int age; char *work; public: Person(){cout<<"Person()"<<endl; this->work=NULL; this->name=NULL; } Person(char *name){ cout<<"Person(char *name)"<<endl; this->name=new char[strlen(name)+1]; strcpy(this->name,name); this->work=NULL; } Person(char *name,int age,char *work="none"){ cout<<"Person(char *name,int age)"<<endl; this->age=age; this->name=new char[strlen(name)+1]; strcpy(this->name,name); this->work=new char[strlen(work)+1]; strcpy(this->work,work); } ~Person() { cout<<"~Person()"<<endl; if(this->name) { cout<<this->name<<"----"<<endl; delete this->name; } if(this->work) { delete this->work; } } void printfInfo(void) { cout<<"name="<<name<<" age="<<age<<" work="<<work<<endl; } }; int main() { Person Per("chenmiaohong",16); Person Per2; Person Per3(); Person *per4=new Person;///调用无参数构造函数 Person *per5=new Person();//调用无参数构造函数 Person *per6=new Person[2]; Person *per7=new Person("ls",18,"stu"); Person *per8=new Person("ww",16); Per.printfInfo(); per7->printfInfo(); per8->printfInfo(); delete per4; delete per5; delete []per6; delete per7; delete per8; }

析构函数在对象销毁前的瞬间被调用。 Person *per7=new Person(“ls”,18,”stu”); delete per7; new创建的对象，必须用delete函数销毁掉，负责不会调用析构函数。 Person Per(“chenmiaohong”,16); Person *Per7=new Person(“ls”,18,”stu”); delete Per7; 调用~Person的顺序为先new对象被释放，接着按构造顺序相反的顺序释放，先创建的后调用析构函数。 默认拷贝构造函数 Person per(“zhangsan”,18); Person per2(per); 调用默认的拷贝构造函数将per的值传递给per2，但是这样引入问题因为per与per2指向内存的同一块地址，当对象被销毁时，都会去释放这块内存。 拷贝构造函数实现

Person(Person &per){ cout<<"(Person &per)"<<endl； this->age=per.age; this->name=new char[strlen(per.name)+1]; strcpy(this->name,per.name); this->work=new char[strlen(per.work)+1]; strcpy(this->work,per.work); } int main() { Person per("zhangsan",18); Person per2(per); per2.printfInfo(); return 0; }

类的静态成员

类成员必须通过类的对象来访问，不能通过类名直接访问。如果将类的成员定义为静态成员，则允许使用类名直接访问，静态成员使用static关键字访问

class Person{ public： static unsigned int m_Price;//静态数据成员通常需要在类外部进行初始化 } unsigned int Person::m_Price=10; 在一个类中类的静态数据成员被类中所有的类对象所共享。不论哪个对象对其值进行了修改。其他对象的静态数据成员也会被修改。 静态数据成员可以是当前类的类型，而其他数据成员只能是当前类的指针或者应用。 class Person{ public: static unsigned int m_price; Person per;//非法的定义，不允许在该类中定义所属类的对象 static Person per1;//正确,静态数据成员允许定义类的所属类对象 Person *per2;//正确，允许定义类的所属类型的指针型对象 } 静态数据成员可以作为成员函数的默认参数，其他数据成员不可以 class Person() { public: static unsigned int m_per; int m_page; void OutputInfo(int data=m_per)//正确，静态数据成员作为函数的默认参数 { cout<<data<<endl; } void OutputPage(int page=m_page)//错误 { cout<<page<<endl; } }

类的静态成员函数只能访问静态数据成员，不能访问非静态数据成员。 static void Outputinfo()const；错误的定义，静态成员函数末尾不能使用const关键字 在类中定义的静态成员函数，在类外实现时不能添加static关键字

对象的构造顺序

构造顺序：按运行中定义对象的顺序调用构造函数，静态对象只调用一次构造函数; 全局对象在main函数执行前被构造

Person per_g("per_g",10);1 void fun() { Person per_func("per_func",11);4 static Person per_func_s("per_func_s",11);5 } int main() { Person per_main("per_main",11);2 static Person per_main_s("per_main_s",11);3 for(int i=0;i<2;i++) { fun(); Person per_for("per_for",i);6 } return 0; }

析构函数调用顺序：

局部普通类对象，主函数内对象，局部static对象，main函数static对象，全局static对象

Person(char *name,int age,char *work="none"){ cout<<"Person(char*,int),name="<<name<<",age="<<age<<endl; this->age=age; this->name=new char[strlen(name)+1]; strcpy(this->name,name); this->work=new char[strlen(work)+1]; strcpy(this->work,work); } ...... class Student{ private: Person father; Person mother; int stu_id; public : Student() { cout<<"Student()"<<endl; } Student(int id,char *father,char *mother,int father_age=40,int mother_age=39):father(father,father_age),mother(mother,mother_age)使用父类的构造函数 { cout<<"Student(int id,char *father,char *mother,int father_age=40,int mother_age=39)"<<endl; } }; int main() { Student s(10,"cath","lily"); return 0; }

构造函数调用顺序是：先调用father、mother、stu 析构函数调用顺序是：先调用stu、mother、father