Question about structs in class which wouldn't save value.

[hayloiuy]

I have a question about this particular code.
The structs would not save the value entered by the user into its class' attributes.
If you do not understand what i am talking about, please compile the code below. Can someone kindly explain what is the problem and how to fix it? Thank you for your time.

#include <iostream>
#include <string>

using namespace std;

class Sam
{
    struct sample{
        int a;
        string b;
        };

    public:

        void set_a();
        void set_b();
        int ret_a();
        string ret_b();
};


void Sam::set_a()
{
    int a1;
    cout<<"Insert int a";
    cin>>a1;
    sample().a=a1;
}

int Sam::ret_a()
{
    return sample().a;
}

void Sam::set_b()
{
    string b1;
    cout<<"Insert string b";
    cin>>b1;
    sample().b=b1;
}

string Sam::ret_b()
{
    return sample().b;
}

int main()
{
    Sam c;

    c.set_a();
    c.set_b();

    cout<<c.ret_a()<<endl<<c.ret_b();  //It should output the same value inputted by the user             
                                                             // but it shows nonsense. why is it so?
    return 0;
}

[Paul McKenzie]

Can someone kindly explain what is the problem

What does this line do?

sample().a=a1;

It creates a temporary variable of type "sample". Temporary variables are destroyed as soon as the statement is executed, therefore nothing has happened.

and how to fix it?

You create a member variable.

#include <iostream>
#include <string>

using namespace std;

class Sam
{
    struct sample{
        int a;
        string b;
        };
     
    sample mySampleA, mySampleB;
    public:

        void set_a();
        void set_b();
        int ret_a();
        string ret_b();
};


void Sam::set_a()
{
    int a1;
    cout<<"Insert int a";
    cin>>a1;
    mySampleA.a=a1;
}

int Sam::ret_a()
{
    return mySampleA.a;
}

Regards,

Paul McKenzie

[hayloiuy]

AARGGGHHHH this is just a very very simple mistake which i overlook. I spent 2 hours thinking what is the problem. Imagine that. If there are any thumbs up in this forum i will give you a hundred. Thank you very much and i am very very deeply sorry for wasting your time.

[S_M_A]

If there are any thumbs up

There is... just add :thumb:

[GNiewerth]

Since copying a std::string object might be expensive changing the ret_b() method to

const std::string& Sam::ret_b() const
{
   return b;
}

might be useful, too.