本文共 3994 字,大约阅读时间需要 13 分钟。
C++
int add(int &b){b=b+1;return b;}int main(){int a=99;printf("%d\n",add(a));}
#includeusing namespace std;class Person{private: char *name; int age; char *work;public: Person(){ cout<<"Person()"< name=name; } Person(char *name,int age,char *work="none"){ cout<<"Person(char *name,int age)"< name=name; this->age=age; this->work=work; } void printfInfo(void) { cout<<"name="< <<" age="< <<" work="< < printfInfo(); per8->printfInfo(); delete per4; delete per5; delete []per6; delete per7; delete per8; return 0;}
#include#include using namespace std;class Person{private: char *name; int age; char *work;public: Person(){ cout<<"Person()"< work=NULL; this->name=NULL; } Person(char *name){ cout<<"Person(char *name)"< 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)"< 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()"< name) { cout< name<<"----"< name; } if(this->work) { delete this->work; } } void printfInfo(void) { cout<<"name="< <<" age="< <<" work="< < 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。Person(Person &per){ cout<<"(Person &per)"<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<<
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);1void 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;}
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="<<<",age="< < 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()"<