Remove items from vector on collision? - c++

Question

I am making a simple game in SDL2 where you are a jellyfish who swim around and eat small food. I have done the jellyfish and got some food spread out on the screen. I have a vector with all the foods (which are part of a class called Entity). Every iteration of the game loop I want to iterate through the vector and check if the foods collide with the player, but with what I've got it gets wierd.
The for loop where I create schools of food and then foods who originate from the school position.
std::vector<Entity> entities;
for (int i = 0; i < 30; i++)
{
int foodg_x = rand() % winW;
int foodg_y = rand() % winH;
for (int i = 0; i < 20; i++)
{
Entity entity = Entity(foodTexture, 1, 1, foodg_x + rand() % 100, foodg_y + rand() % 100, 4, 4);
entities.push_back(entity);
}
}
Here is the for loop in the while loop where the iteration happens. Every Entity has an x and a y variable, and the player position is located at plr.x and plr.y. Right now it only checks if the foods are under and left of the player, but nothing disappears:
for (int i = 0; i < entities.size(); i++)
{
if (entities[i].x < plr.x && entities[i].y > plr.y)
{
std::cout << "c";
entities.erase(entities.begin() + i);
}
else
{
i++;
}
SDL_RenderCopy(renderer, entities[i].texture, &entities[i].srcRect, &entities[i].dstRect);
}
What is going on here and how could I fix this?

Answer 1

I fixed it! It had pretty much nothing to do with the loop. The problem was that the x and y variables of the entities were all the same, although not in their respective rects.
This was fixed by changing
Entity::Entity(SDL_Texture* tex, int srcW, int srcH, float x, float y, int w, int h)
{
texture = tex;
x = x;
y = y;
w = w;
h = h;
srcRect.x = 0;
srcRect.y = 0;
srcRect.w = srcW;
srcRect.h = srcH;
dstRect.x = x;
dstRect.y = y;
dstRect.w = w;
dstRect.h = h;
}
To:
Entity::Entity(SDL_Texture* tex, int srcW, int srcH, float ex, float ey, int ew, int eh)
{
texture = tex;
x = ex;
y = ey;
w = ew;
h = eh;
srcRect.x = 0;
srcRect.y = 0;
srcRect.w = srcW;
srcRect.h = srcH;
dstRect.x = x;
dstRect.y = y;
dstRect.w = w;
dstRect.h = h;
}
If someone could, please explain why this is. :)