#include <cstdlib>
#include <iostream>
#include <vector>
using namespace std;
class object{
public:
object(){
//cout << "object created \n";
}
void update(){
cout << "OBJECT!!!" << "\n";
}
void setCost(int newCost){}
};
vector<object> objectVector;
vector<object>::iterator objectIterator;
class fruit: public object{ //EXTENDS OBJECT
float fruitCost;
public:
fruit(){ //Constructor
//cout << "fruit created \n";
}
fruit(float newFruitCost){ //Overload Constructor, uses this if param met
fruitCost = newFruitCost;
cout << "fruit created OVERLOAD\n";
}
void setCost(float newFruitCost){
fruitCost = newFruitCost;
}
float getCost(){
return fruitCost;
}
void update(){
cout << fruitCost << "\n";
}
};
int main(){
objectVector.push_back(fruit(0)); //create a null one that isnt counted
float input;
while (1){
cout << ":";
cin >> input;
if (input == 0){ //ITERATE
for (objectIterator = objectVector.begin()+1;
objectIterator != objectVector.end();
objectIterator++) {
objectIterator -> update();
}
}else{ //CREATE A NEW FRUIT
objectVector.push_back(fruit(input));
/* USE THIS FOR GRABBING THE RECENTLY MADE ONE
objectIterator = objectVector.end()-1;
objectIterator -> setCost(y);
*/
}
}
system("PAUSE");
return 0;
}
Inheritance Problems
Author
Alright, so im messing around with some stuff in C++, and I have a question reguarding vectors etc. etc.
Now in the above code, if you enter the input 1, 2, and 3 then 0 you get 3
OBJECT!!! lines, now what I want is to hold all my objects in one vector, as if the following
vector<object> objectVector;
vector<object>::iterator objectIterator;
is changed to
vector<fruit> objectVector;
vector<fruit>::iterator objectIterator;
Then it works how I want it to, it outputs the cost, but declaring a vector etc. etc. for each class I might have in a game just seems redundant... is what I want even possible? Is there a better way to code the above?
Thanks!
Ummm. I think that you have a "shadowing" problem. You need to make you functions in your parent class "virtual" so that they do not *shadow* fruits functions.
Author
Thanks for the reply, but when I add virtual to my object member function update, it still does the same thing...
But I did some research on virtual more, am I correct in saying that its b/c my pointer isnt pointing at "fruit"? Ive been trying to implement pointers to the iterating, but so far I havent had much luck. :(
But I did some research on virtual more, am I correct in saying that its b/c my pointer isnt pointing at "fruit"? Ive been trying to implement pointers to the iterating, but so far I havent had much luck. :(
Ok Im actually relatively new to C++ so this definition may not be exactly correct - and someone PLEASE CORRECT ME IF IT ISN'T!!!.
This is what i think is happening:
You have a vector of objects. Each position in your vector is only allocated enough memory for a single "object" object(lol). But a "fruit" object is larger than an "object" object because it is a subclass. So when you try to add a "fruit" object into your vector, it is getting sliced back to the size of an "object" object. Thus all your objects in your vector are actually of type "object".
Solution:
Pointers are all the same size. So create a vector<object *> instead. Now you will have to go "push_back(new fruit(x))" when adding items to your vector. So now you are just adding a pointer to a new "fruit" object, which is the same size as a pointer to an "object" object.
update() still needs to be virtual
Hope that helps.
This is what i think is happening:
You have a vector of objects. Each position in your vector is only allocated enough memory for a single "object" object(lol). But a "fruit" object is larger than an "object" object because it is a subclass. So when you try to add a "fruit" object into your vector, it is getting sliced back to the size of an "object" object. Thus all your objects in your vector are actually of type "object".
Solution:
Pointers are all the same size. So create a vector<object *> instead. Now you will have to go "push_back(new fruit(x))" when adding items to your vector. So now you are just adding a pointer to a new "fruit" object, which is the same size as a pointer to an "object" object.
update() still needs to be virtual
Hope that helps.
One other thing:
1)Because you have a vector of pointers, you will need to dereference your iterator and then do the indirection operator thing(i dont know what its called) to access your update() function on your object:
(*objectIterator)->update();
1)Because you have a vector of pointers, you will need to dereference your iterator and then do the indirection operator thing(i dont know what its called) to access your update() function on your object:
(*objectIterator)->update();
This topic is closed to new replies.
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