Error with const member in class

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?

It appears that you continued to write code after introducing this error; never add to code that doesn't work. It also appears that you are attempting a complicated exercise before you have mastered the basics. What do you expect the assignment (std::string adr=address.aString;) to do? When do you expect it to be executed? — Beta
– Beta, Commented Oct 13, 2015 at 2:51
@immibis - he changed the file, like I suggested in the first comment, but not the problem. It was a valid edit — chrisb2244
– chrisb2244, Commented Oct 13, 2015 at 3:21

Community · Accepted Answer · 2020-06-20 09:12:55Z

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.

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