CODEWITHSUNDEEP
c++debuggingpointersvectorstl
Computernerd
Computernerd

Reputation: 7762

How to iterate through a vector of class pointer

I have a class User

class User
{
        public:
            User();
            User(string, string);
            virtual string getRole();

            void setPW(string);
            void setID(string);
            string getPW();
            string getID();

        protected:
            string id;
            string pw;
};

And several subclasses which inherit from User

class Customer : public User
{
        public:
            Customer();
            Customer(string, string,string,string, string, string, string, string, string);

                        virtual string getRole();
                        string getSname();
                        string getFname();
                        string getTitle();
                        string getAddress();
                        string getTown();
                        string getCity();
                        string getPostalCode();

                        void setSname(string);
                        void setFname(string);
                        void setTitle(string);
                        void setAddress(string);
                        void setTown(string);
                        void setCity(string);
                        void setPostalCode(string);




        private:
            string sname;
            string fname;
            string title;
            string address;
            string town;
            string city;
            string postalcode;
};

All the information is stored inside a vector which contains pointers to the class User

 vector<User*> userVector

How do i iterate through the vector of pointers to a class and call the respective methods of the class ??

If its a vector of User object , i can declare an iterator vector<User>::iterator p , is there something equivalent for pointers to a object and how do i call the respective method of the class depending on the object

EDIT , this is what i have tried 

vector<User*>::iterator p;

    p=userVector.begin();

    while ( p != userVector.end() )
    {

        //how to dereference
        p++;
    }

Upvotes: 1

Views: 3989

Answers (3)

Kaje
Kaje

Reputation: 851

I recommend following 3 solutions in its priority order. You can select whatever you are comfortable with.

  1. If you are using C++11 features, you can use range based loops for easy syntax. That's always advisable too.

  2. Use for_each loop.

  3. Otherwise, use like this which would be more optimal. 

    for( vector<User*>::iterator itr = userVector.begin(), itr_end = userVector.end(); itr != itr_end; ++itr )
{
    std::cout << (*itr)->getRole() << std::endl;
}

Here you are not going to receive the end iterator each iteration of loop traversal.

Upvotes: 3

jrok
jrok

Reputation: 55415

Iterators behave like pointers in the way that they can be dereferenced and incremented (other operations depend on iterator category).

If you have a vector of pointers, then dereferencing its iterator gives you a pointer. That means you need to dereference once more to get to members. Assuming it is the iterator:

    (*it) -> getID()
//  ^     ^^
//  |     second dereferencing
//  first dereferencing

Upvotes: 1

benjymous
benjymous

Reputation: 2122

An iterator basically functions like a pointer, so you can consider vector<TYPE>::iterator to be the equivalent of TYPE*

This means vector<TYPE*>::iterator equates to TYPE**

So to get at your functions, you just need to dereference the iterator:

for( vector<User*>::iterator iter = userVector.begin(); iter != userVector.end(); ++iter )
{
    std::cout << (*iter)->getRole() << std::endl;
}

Upvotes: 1

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