Calling constructor from within member function?

[Jsel]

I am trying to make a member function for my class that lets the user input all of the values for the object's variables. When I try to use the constructor inside this function, it does not assign anything new to the variables that were already initialized when the object itself was created. Is there a correct way to do this?

 25     void Administrator::get_all_data()
 26     {
 27         string a_name, a_number, a_title, a_department, a_supervisor;
 28         double a_salary;
 29         cout << "\nEnter name: "; cin >> a_name;
 30         cout << "Enter ssn: "; cin >> a_number;
 31         cout << "Enter title: "; cin >> a_title;
 32         cout << "Enter department: "; cin >> a_department;
 33         cout << "Enter supervisor name: "; cin >> a_supervisor;
 34         cout << "Enter weekly salary: "; cin >> a_salary;
 35         Administrator(a_name, a_number, a_salary, a_title, a_department, a_supervisor);
 36         cout << department;
 37     }

for example, when the function gets to line 36, I can see that department has not changed after the constructor call.

[webJose]

You cannot call constructors directly. If you do, you just create a new object (not alter the current one). Just assign the member fields manually one by one.

[Jsel]

Ok, thank you webJose.

[Disch]

Another way to do it would be to copy the object:

void Administrator::get_all_data()
{
    // .. get all that stuff
    *this = Administrator(...);
}

This works by constructing a new temporary Administrator, then copying it to 'this' Adminstrator by using the assignment operator.

[D80DSL3A]

Why do you cin to local variables? Why not cin to the data members directly?
eg: Instead of cout << "Enter department: "; cin >> a_department;
then trying to copy a_department to department
just make the assignment:
cout << "Enter department: "; cin >> department; and likewise for the other data members?

What am I missing here?

Sometimes I write a function that mirrors the constructor so I can conveniently assign the data member values. Two cases where this is useful:
1) An array of objects was allocated using the default constructor.
2) An objects values are to be re-assigned.

[jsmith]

One reason to not read into the member variables directly, which is not accounted for in the above code, is to provide a strong exception guarantee.