第--章━━构造函数和析构函数优秀文档.ppt

C++程序设计主要内容对象的初始化━━使用初始化数据列表对象的初始化━━使用构造函数构造函数构造函数━━在函数体中对各成员数据赋初值【例】（时钟类、构造函数重载）
#include<iostream.h>
classClock
{inthour,minute,second;
public:
Clock()
{hour=0;minute=0;second=0;cout<<“调用不带参的构造函数!\n”;}
Clock(inth,intm,ints)
{hour=h;minute=m;second=s;cout<<“调用带3个参的构造函数!\n”;}
voidsettime(inth,intm,ints)
{hour=h;minute=m;second=s;}
voidshowtime()
{cout<<hour<<“:”<<minute<<“:”<<second<<endl;}
};
voidmain()
{Clockc1,c2(10,20,30);
c1.showtime();
c2.showtime();
c2.settime(8,50,20);
c2.showtime();}【例】（矩形类、带默认形参值的构造函数）
#include<iostream.h>
#include<math.h>
classRectangle
{floatleft,top,right,bottom;
public:
Rectangle(floatL=0,floatT=0,floatR=0,floatB=0)
{left=L;top=T;right=R;bottom=B;}
voidset(floatL,floatT,floatR,floatB)
{left=L;top=T;right=R;bottom=B;}
voidprint()
{cout<<“left=”<<left<<“\ttop=”<<top<<‘\t’;
cout<<“right=”<<right<<“\tbottom=”<<bottom<<‘\t’;
cout<<“面积=”<<fabs(right-left)*fabs(bottom-top)<<endl;}};
voidmain()
{Rectangler0;r0.print();
Rectangler1(10);r1.print();
Rectangler2(10,20);r2.print();
Rectangler3(10,20,30);r3.print();
Rectangler4(10,20,30,40);r4.print();
r0.set(1,2,3,4);r0.print();}默认的构造函数默认的构造函数默认的构造函数this指针━━成员函数中指向当前对象的指针this指针━━成员函数中指向当前对象的指针【例】（学生类、this指针）
#include<iostream.h>
#include<string.h>
classStudent
{intid;
charname[8];
intscore;
public:
Student(inti,char*na,ints)
{id=i;strcpy(name,na);score=s;
cout<<“对象地址=”<<this<<“\t调用构造函数了!\n”;}
voidprint()
{cout<<“学号:”<<id<<“\t姓名:”<<name<<“\t成绩:”<<score<<endl;}
};
voidmain()
{Students1(111,“张军”,99);
Students2(222,“王红”,88);
s1.print();
s2.print();}对象的生存期和作用域【例】（矩形类、构造函数重载、全局对象、static局部对象、auto局部对象）
#include<iostream.h>
classRectangle
{floatleft,top,right,bottom;
public:
Rectangle(floatL,floatT,floatR,floatB)
{left=L;top=T;right=R;bottom=B;cout<<“调用带4个参的构造函数!\n”;}
Rectangle(floatL,floatT,floatR)
{left=L;top=T;right=R;bottom=0;cout<<“调用带3个参的构造函数!\n”;}
Rectangle(floatL,floatT)
{left=L;top=T;right=0;bottom=0;cout<<“调用带2个参的构造函数!\n”;}
Rectangle(floatL)
{left=L;top=0;right=0;bottom=0;cout<<“调用带1个参的构造函数!\n”;}