Initialization of vector variables in default constructor?

Question

How do I initialize private string variables name and age in my constructor to "John", and 30?

class Name_pairs
{
public:
    Name_pairs();
    Name_pairs(string name_cons, double age_cons);
    vector <string> read_names() {return name;};
    vector <double> read_ages() {return age;};
    void print();
    void sort();

private:
    vector <string> name;
    vector <double> age;
};

Name_pairs::Name_pairs()
    : name(), age()
{}

The usual :private_variable(default value) doesn't work. Sorry if noobish question, first time encountering classes.

you don't need vector for name and age if Name_pairs serve for one person only. — billz
– billz, Commented Apr 10, 2015 at 11:22
Besides you not needing vectors, just abut any book or tutorial should have told you how to initialize member variables in a constructor. — Some programmer dude
– Some programmer dude, Commented Apr 10, 2015 at 11:25

Mr.Yellow · Accepted Answer · 2015-04-10 11:33:21Z

1

you try to initialize the vector name with a string. These are 2 different data types. As billz already suggested, you won't need a vector of strings for a name_pair (or your class naming is misleading for billz and for me). If you would declare name as a string, you could use the constructor's initialization list again.

...
private:
    string name;
    double age;
};

Name_pairs::Name_pairs(string name_cons, double age_cons)
    : name(name_cons), age(age_cons)
...

When you have just named your class ambigous and you really need a vector of strings in your class and you only get strings as constructor parameters, you will have to add those strings in the constructors body into your vectors.

Name_pairs::Name_pairs(string name_cons, double age_cons)
{
  name.push_back(name_cons);
  age.push_back(age_cons);
}

answered Apr 10, 2015 at 11:33

Mr.Yellow

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1 Comment

Luka Over a year ago

It's part of the task I'm doing. It could be I misunderstood it, but it does say to use strings as variabbles. This code also works, thank you!

nils · Accepted Answer · 2015-04-10 11:24:20Z

1

Like so:

Name_pairs::Name_pairs()
    : name( 1, "John" ), age( 1, 30 )
{}

answered Apr 10, 2015 at 11:24

nils

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1 Comment

nils Over a year ago

@Luka This creates a vector of length 1 and initializes all elements to "John" or 30, respectively. This makes more sense if your vector is initialized with many elements, but it also works if it's only one.

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