'this' argument has type const but function is not marked const

Question

Okay so I'm a bit of a noob at C++ and in my second assignment I am required to make classes with public and private arguments etc, etc. Basically the mutator functions won't work because apparently they're not of type const?

This is the header file with the class:

class Customer {

private:
    string PhoneNumber_;
    string Name_;
    string Address_;

public:
    string get_PhoneNumber() const {return PhoneNumber_;} // Accessor
    const void set_PhoneNumber(unsigned x) {PhoneNumber_ = x;} // Mutator

    string get_Name() const {return Name_;}
    const void set_Name(unsigned x) {Name_ = x;}

    string get_Address() const {return Address_;}
    const void set_Address(unsigned x)  {Address_ = x;}
};

// declare the CreateCustomer function prototype with default values
Customer* CreateCustomer(const string& id = BLANK, const string& name = BLANK, const string& address = BLANK);

Customer* CreateCustomer(const string& id, const string& name, const string& address) {
    Customer* temp = new Customer();

    temp->get_PhoneNumber() = id; // Due to the Accessors and Mutators PhoneNumber, Name and Address are now functions
    temp->get_Name() = name;
    temp->get_Address() = address;

    return temp;
}

And this is the error I get in the main.cpp file:

cout << "\n\nDear ";
    cout << Charge[0].Holder.set_Name() << " (" << Charge[0].Holder.set_PhoneNumber() << ")";  //  DisplayCustomer(customer) ;

    cout << ",\n" << Charge[0].Holder.set_Address() << "\n\n"

Basically, the exact error message is:

Member function 'set_Name' not viable: 'this' argument has type 'const Customer', but function is not type const

It happens with set_PhoneNumber and set_Address as well. Any help would be greatly appreciated! Thanks!

UPDATE: I got it working. Thanks everyone for helping me out!

Answer 1

If you want to set a value, use the set method. get Methods are only to obtain variables, not to set the inner variables of a class (If they are defined the way you did).

The correct usage is:

Customer* CreateCustomer(const string& id, const string& name, const string& address) {
    Customer* temp = new Customer();

    temp->set_PhoneNumber( id );
    temp->set_Name( name );
    temp->set_Address( address );

    return temp;
}

Also, you have to alter the interface of your methods:

class Customer {

private:
    string PhoneNumber_;
    string Name_;
    string Address_;

public:
    string get_PhoneNumber() const {return PhoneNumber_;} // Accessor
    void set_PhoneNumber(const string& x) {PhoneNumber_ = x;} // Mutator

    string get_Name() const {return Name_;}
    void set_Name(const string& x) {Name_ = x;}

    string get_Address() const {return Address_;}
    void set_Address(const string& x)  {Address_ = x;}
};

Since you want to set strings and not numbers.

Using const string& as function arguments is better than string to not copy the string when passing it as an argument. Since it is a const reference, you don't have to fear the function could manipulate the input.