C++重载运算符练习--对people类重载“= =”运算符和“＝”运算符

#include<iostream>
#include<string>
using namespace std;
class Data{
public:
    Data(){}
    Data(int yy,int mm,int dd){
    year=yy;
    month=mm;
    day=dd;
    }
    Data(Data &ap){
        year=ap.year;
        month=ap.month;
        day=ap.day;
    }
    ~Data(){
    }
    int get_year(){
        return year;
    }
    int get_month(){
        return month;
    }
    int get_day(){
        return day;
    }
    void set_year(int y){
        year=y;
    }
    void set_month(int m){
        month=m;
    }
    void set_day(int d){
        day=d;
    }
private:
    int year;
    int month;
    int day;
};
class People{
public:
    People(int num,string se,Data birth,string iid):birthday(birth){
        number=num;
        sex=se;
        id=iid;
    }
    People(People &tp){
        number=tp.get_number();
        sex=tp.get_sex();
        id=tp.get_id();
        birthday=tp.get_birthday();
    }
    People(){}
    People get_People(){
        int num,yy,mm,dd;
        string ID,se;
        cout<<"Please enter the number of the People:"<<endl;
        cin>>num;
        cout<<"Please enter the sex:(male or female)"<<endl;
        cin>>se;
        cout<<"Please enter the birthday:"
            <<"(Warning the format is 1998 8 3.)"<<endl;
        cin>>yy>>mm>>dd;
        cout<<"Please enter the id:"<<endl;
        cin>>ID;
        Data birth(yy,mm,dd);
        id=ID;
        number=num;
        sex=se;
        birthday=birth;
        return *this;
    }
    ~People(){}
    void set_number(int num){
        number=num;
    }
    void set_sex(string se){
        sex=se;
    }
    void set_birhtday(Data birth){
        birthday=birth;
    }
    void set_id(string iidd){
        id=iidd;
    }
    inline int get_number(){
        return number;
    }
    inline string get_sex(){
        return sex;
    }
    Data get_birthday()
    {
        return birthday;
    }
    inline string get_id(){
        return id;
    }
    void details(){
        cout<<"Number:"<<number<<endl;
        cout<<"Sex:"<<sex<<endl;
        cout<<"Birthday:"<<birthday.get_year()<<"/"<<birthday.get_month()<<"/"<<birthday.get_day()<<endl;
        cout<<"ID:"<<id<<endl;
    }
    People& operator=(const People &p1){
        if(this==&p1){
            return *this;
        }
        number=p1.number;
        sex=p1.sex;
        birthday=p1.birthday;
        id=p1.id;
    }
private:
    int number;
    string sex;
    Data birthday;
    string id;
    friend bool operator== (const People &p1,const People &p2){
        if(p1.id==p2.id)
            return true;
        else
            return false;
    }
};
int main()
{
    People asp,tcp,tmp;
    asp.get_People();
    asp.details();
    tcp.get_People();
    tcp.details();
    if(asp==tcp)
        cout<<"The id of two people is common!!!"<<endl;
    else
        cout<<"The id of two people is different!!!"<<endl;
    tmp=asp;
    tmp.details();
    return 0;
}