Question

My base class:

class Item
{
protected:  
    int count;
    string model_name;
    int item_number;

public:
    Item();
    void input();
}

My derived Class:

class Bed : public Item
{
private:
    string frame;
    string frameColour;
    string mattress;

public:
    Bed();
    void input();
}

for now all my input function is trying to do is output which method is being used:

void Item::input()
{ 
    cout<<"Item input"<<endl;
}

void Bed::input()
{
    cout<<" Bed Input"<<endl;
}

when I call the function in main I’d like the derived class input to be used but at present the item input is.

Main:

vector<Item> v;
Item* item;
item= new Bed;
v.push_back(*item);
v[count].input();
count++;

I have followed the method laid out in a book I have but I think i may be confused about how to create new objects stored in the vector.

Any help would be great,
Thanks
Hx

Answer 1

You haven’t marked your method as virtual.

Also, because you have a vector of objects, not pointers, you’ll run into object slicing. Although it will compile, it isn’t correct.

The proper way is having a vector of pointers or smart pointers.

class Item
{
   //....
   virtual void input(); //mark method virtual in base class
};

class Bed : public Item
{
   //....
   virtual void input();
};


vector<Item*> v;
Item* item = new Bed;
v.push_back(item);
//...
//remember to free the memory
for ( int i = 0 ; i < v.size() ; i++ ) 
    delete v[i];