Question

C++错误提示 error LNK2001:unresolved external symbol "public: __thiscall People::People(void)求解

#include<iostream>
using namespace std;
class Date{
public:
Date(int y=0,int m=0,int d=0){
year=y;mouth=m;day=d;}
Date(Date &d);
void set(){
cin>>year>>mouth>>day;}
void output(){
cout<<year<<" "<<mouth<<" "<<day<<endl;}
private:
int year,mouth,day;
};
Date::Date(Date &d){
year=d.year;mouth=d.mouth;day=d.day;
cout<<"Caling the copy constructer of Date"<<endl;}
class People{
public:
People();
People(Date b,char i[18],int n=0,int y=0,int m=0,int d=0,int s=0):birthday(y,m,d){
number=n;sex=s;strcpy(id,i);}
People(People &p);
void set(){
cout<<"编号"<<endl;cin>>number;
cout<<"性别(1or2)"<<endl;cin>>sex;
cout<<"身份证"<<endl;cin>>id;
cout<<"出生日期"<<endl;birthday.set();
cout<<"信息已录入"<<endl;}
void output(){
cout<<"编号"<<number<<endl;
if(sex=1)cout<<"男"<<endl;
else cout<<"女"<<endl;
cout<<""<<id<<endl<<""<<endl;;
birthday.output();}
~People(){cout<<"END"<<endl;}
private:
int number,sex;
char id[18];
Date birthday;};
People::People(People &p){
number=p.number;
sex=p.sex;
birthday=p.birthday;
strcpy(id,p.id);}
int main(){
Date d(2005,5,6);
People p;
p.set();
p.output();
return 0;
}
最后提示error LNK2001: unresolved external symbol "public: __thiscall People::People(void)" (??0People@@QAE@XZ)
求解

Answer 1

只声明了函数 却没有实现，你加上实现就行了 People(){};

Answer 2

People::People(); 没有定义啊，只有声明

People p; 调用的是 People::People()，不是其他的构造函数