How can I add different names to a vector using classes? - c++

Question

#include <iostream>
#include <string>
#include <vector>
class Enemy
{
private:
std::string rank = "Boss";
std::string rank2 = "Miniboss";
public:
std::string type;
std::string get_rank(){
return rank;
}
std::string get_rank2(){
return rank2;
}
};
int add_enemy(std::vector<Enemy>&enemies, Enemy enemy) // I wanna pass by reference because I want to modify the vector
{
for(size_t i; i < enemies.size(); i++) {
if(enemies.at(i).type == enemy.type){ // here I'm saying, if I add an enemy that's of the same type, I don't wanna add it anymore
return 1; // it returns an error, because they are the same type, so it shouldn't add it?
}
}
enemies.push_back(enemy);
}
int main()
{
Enemy enemy;
enemy.type = "Dragon";
std::cout << enemy.type << " is a " << enemy.get_rank() << std::endl;
Enemy nrone, nrtwo, nrthree, nrfour, nrfive;
// I want to add these and keep them in a vector
std::vector<Enemy> enemies;
nrone.type = "Orc";
nrtwo.type = "Goblin";
nrthree.type = "Troll";
nrfour.type = "Ogre";
nrfive.type = "Orc";
std::cout << nrfour.type << " is of rank " << nrfour.get_rank2() << std::endl;
enemies.push_back(nrone);
enemies.push_back(nrtwo);
enemies.push_back(nrthree);
enemies.push_back(nrfour);
enemies.push_back(nrfive);
std::cout << add_enemy(enemies, enemy) << std::endl;
return 0;
}
Hi, I am studying Classes & Objects in C++ right now, and I'm trying to achieve the following: create a vector of NPC monsters and add a bunch of monster types to the vector. However, if the monster/enemy is of the same type, I don't want to add it to the vector, but discard it.
In my case, I have two Orcs, so the vector should discard one of the orcs, but it doesn't, and instead if showing me a strange number on the screen.
I tried it this way and I still can't figure it out :( Any solutions?

Answer 1

So the reason that both Orcs are added is because by the time you run add_enemy, you've already added them. All the enemies should be using the add_enemy function instead of push_back:
int main()
{
Enemy enemy;
enemy.type = "Dragon";
std::cout << enemy.type << " is a " << enemy.get_rank() << std::endl;
Enemy nrone, nrtwo, nrthree, nrfour, nrfive;
// I want to add these and keep them in a vector
std::vector<Enemy> enemies;
nrone.type = "Orc";
nrtwo.type = "Goblin";
nrthree.type = "Troll";
nrfour.type = "Ogre";
nrfive.type = "Orc";
std::cout << nrfour.type << " is of rank " << nrfour.get_rank2() << std::endl;
enemies.push_back(nrone); //Add one Orc
enemies.push_back(nrtwo);
enemies.push_back(nrthree);
enemies.push_back(nrfour);
enemies.push_back(nrfive); //Add another Orc
std::cout << add_enemy(enemies, enemy) << std::endl; //The Orcs are already in enemies!
return 0;
}
The reason you're seeing a strange number on the screen is that if you DO successfully add an enemy, the function doesn't return anything:
int add_enemy(std::vector<Enemy>&enemies, Enemy enemy) // I wanna pass by reference because I want to modify the vector
{
for(size_t i; i < enemies.size(); i++) {
if(enemies.at(i).type == enemy.type){
return 1; // Return an error
}
}
enemies.push_back(enemy); //OK, so we added the enemy, but where's the return?
}
Your add_enemies function must return a value, since it is declared as type int.
P.S... consider using a range based loop to make things a little easier:
for(Enemy& existingEnemy: enemies) {
if(enemy.type == existingEnemy.type) {
return 1;
}
}

Answer 2

The main problem is that you are not initializing the loop variable (i) in your add_enemy function (so the loop may never run, or it may skip some elements). Also, that function must return a value (presumably, 0) if the loop ends.
Try this:
int add_enemy(std::vector<Enemy>& enemies, Enemy enemy) // I wanna pass by reference because I want to modify the vector
{
for (size_t i = 0; i < enemies.size(); i++) { /// You forgot to initialize "i"!
if (enemies.at(i).type == enemy.type) { // here I'm saying, if I add an enemy that's of the same type, I don't wanna add it anymore
return 1; // it returns an error, because they are the same type, so it shouldn't add it?
}
}
enemies.push_back(enemy);
return 0; // The function MUST return an int value!
}

Answer 3

The strange number is easily explained. In your function you fail to return anything in the case where you do add the enemy. Add a return value and the strange number will go away.
int add_enemy(std::vector<Enemy>&enemies, Enemy enemy)
{
for(size_t i = 0; i < enemies.size(); i++) {
if(enemies.at(i).type == enemy.type){
return 1;
}
}
enemies.push_back(enemy);
return 0; // added a return value
}
The second problem with two orcs is also easily explained. You didn't use your add_enemy function when you added the orcs, you just used the regular vector push_back method so both orcs got added to the vector. You only used your add_enemy method for the dragon.
Also you fail to initialise i in the loop. I didn't spot that but I've corrected the code above.