如下编译时出现一个错误：在error C2228：

Question

编译时有一个错误：error C2228: left of '.display' must have class/struct/union type习题程序为：#include <iostream>using namespace std;class date{public:date(int,int,int);date(int,int);date(int);date();void display();private:int month;int day;int year;};date::date(int m,int d,int y):month(m),day(d),year(y){}date::date(int m,int d):month(m),day(d){year=2005;}date::date(int m):month(m){day=1;year=2005;}date::date(){month=1;day=1;year=2005;}void date::display(){cout<<month<<"/"<<day<<"/"<<year<<endl;}int main(){date d1(10,13,2005);date d2(12,30);date d3(10);date d4();d1.display();d2.display();d3.display();d4.display();return 0;}

Answer 1

是构造的时候错误
date d1(10,13,2005);
date d2(12,30);
date d3(10);
date d4();
.....

date d4();错了 改为date d4;
用 date d4();的话 编译器把d4理解为一个函数了 其实应该是一个类

Answer 2

cout<<month<<"/"<<day<<"/"<<year<<endl;
这句变量没有定义