Error with const member in class - c++

Question

I have a class named Student with its Name and Address classes.
#ifndef ADDRESS_H
#define ADDRESS_H
//This is address class
#include <string>
class Address{
public:
Address(std::string street, std::string city, std::string state, std::string zip) :
street(street), city(city),state(state),zip(zip)
{}
std::string street,city,state,zip;
std::string aString;
aString=street+city+state+zip;
//private:
};
#endif
and the Name class is
#ifndef NAME_H
#define NAME_H
#include <iostream>
#include <string>
class Name {
friend std::ostream &operator <<(std::ostream &os, const Name &name) {
if(name.middle!="")
os << name.last << ", "<<name.middle<<" ," << name.first;
else
os<< name.last <<", "<<name.first;
return os;
}
public:
Name(std::string last, std::string middle, std::string first) : last(last), first(first),middle(middle) {}
private:
std::string last, first, middle;
};
#endif
And the Student class is like:
#ifndef PERSON_H
#define PERSON_H
#include <iostream>
#include <string>
#include "name.h"
#include "Address.h"
class Person {
friend std::ostream &operator <<(std::ostream &os, const Person &person);
public:
Person(const Name &name, int age, const Address &address);
Address address;
std::string adr=address.aString;
//private:
Name name;
int age;
};
#endif
Finally, to call them.
#include <iostream>
#include "student.h"
#include <string>
using namespace std;
Person::Person(const Name &name, int age, const Address &address) : name(name), age(age),address(address) {}
ostream &operator <<(ostream &os, const Person &person) {
os << person.name << " " << person.age<<person.adr;
return os;
}
#include <iostream>
#include "student.h"
using namespace std;
int main() {
Person p(Name("Doe","","Jane"), 21, Address("Park Ave","New York","NY","10002"));
Person p2(Name("Bane","IHateM","Jane"), 21, Address("Bay parkway","Brooklyn","NY","11223"));
cout << p<<endl;
cout<< p2<<endl;
return 0;
}
However, there are some errors during compilation.
(1) The following line is wrong based on complier, how to fix it please?
std::string adr=address.aString;
(2) In my address class, the compiler said that "string does not name a type Error", but following this Why am I getting string does not name a type Error? can't fix the problem, why is that?

Answer 1

Simple Solution
The simplest solution is to move your aString=street+city+state+zip; inside the Address constructor.
Do the same for your adr = ... statement (you'll still need a 'declaration' for std::string adr; within your class header).
To understand why what you wrote won't work, consider this:
When you write (within a class declaration, like in your header)
class myClass
{
int a = 5;
};
you assign a default value to the int a that you have declared - this is both declaration and (default) assignment.
When you write
class Address{
public:
Address(std::string street, std::string city, std::string state, std::string zip) :
street(street), city(city),state(state),zip(zip)
{}
std::string street,city,state,zip;
std::string aString;
aString=street+city+state+zip;
};
you're trying to give a default assignment to aString, but this is invalid code.
You could do this using
std::string aString = ...;
but not
std::string aString;
aString = ...;
because the last line is a 'statement' - something to be executed.