CODEWITHSUNDEEP
c++inheritanceinitialization
James Warner
James Warner

Reputation: 147

C++ - Problems with inheritance and initialization

I have 2 separate code files. One is a main file and one is a file which includes functions.

The code can be viewed below:

Student.cpp

Student::Student(const string &name, int regNo) : Person(name)
{
    map<string, float> marks;
    this->name = name;
    this->regNo = regNo;
}

int Student::getRegNo() const
{
    return regNo;
}

void Student::addMark(const string& module, float mark)
{
    map<string, float>::const_iterator it;
    marks.insert(make_pair(module, mark));

    for (it = marks.begin(); it != marks.end(); it++)
    {
        if(it->second !=0){
            marks[module] = mark;
        }
    }


}

main.cpp

Student stud(name, i);//this is what I want to do

    if(wordfile.is_open() && file2.is_open())
    {
        if(!wordfile.good() || !file2.good())
        {
            cout << "Error reading from file. " << endl;
        }



        while(wordfile.good())
        {
            getline(wordfile, s1);
            istringstream line(s1);
            line >> i;
            line >> name;

            Student stud(name, i);
            cout << stud.getRegNo() << endl;
            itR.push_back(stud.getRegNo());
            vS.push_back(stud);
        }
        wordfile.close();



        while(file2.good())
        {
            getline(file2, s2);
            istringstream line(s2);
            line >> reg;
            line >> mod;
            line >> mark;
                    stud.getRegNo();
        }
        file2.close();
    }
}

What I ideally want to do is use the constructor in my student.cpp to create a student object. I then want to be able to make calls to functions in student.cpp anywhere in my main. However, the values that I need to provide to the constructor come from a file called 'wordfile' in my code. Therefore Student stud(name, i); is being called in the while look for 'wordfile'. However, I then wish to call 'stud.getRegNo()' in the while loop for 'file2', but of course this won't be allowed. As stud is being used as a local variable so its scope doesn't reach that far.

So my question is, is there anyway that I can carry out what I want to do? Maybe by initializing Student stud and then called stud(name, i) then stud.getRegNo()? Or something along those lines?

Upvotes: 0

Views: 129

Answers (2)

stoper
stoper

Reputation: 186

Instead of using vectors (?), what you probably need is a std::map so that you know which student to pick.

    std::map<int, Student*> students;
    while(wordfile.good())
    {
        getline(wordfile, s1);
        istringstream line(s1);
        line >> i;
        line >> name;

        students[i] = new Student(name, i);
    }
    wordfile.close();



    while(file2.good())
    {
        getline(file2, s2);
        istringstream line(s2);
        line >> reg;
        line >> mod;
        line >> mark;

        students[reg]->addMark(mod, mark);
    }
    file2.close();

    ....

Upvotes: 0

sqreept
sqreept

Reputation: 5534

You could allocate Student on the heap using new and keep the instance at a scope level accessible by both contexts.

Student* s;

{ //Context 1
    s = new Student();
}

{ //Context 2
    int regNo = s->getRegNo();
}

Upvotes: 2

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