list.remove_if() crashing the program - c++

Question

I'm working on a game and I'm trying to add collectables. I'm trying to remove the object from the list after the player has collided with it, but it ends up crashing and says:
Unhandled exception thrown: read access violation.
__that was 0xDDDDDDE9.
It says this on the for loop statement, but I think it has to do with the remove_if() function.
Here is my code:
for (sf::RectangleShape rect : world1.level1.brainFrag) {
collides = milo.sprite.getGlobalBounds().intersects(rect.getGlobalBounds());
if (collides == true) {
world1.level1.brainFrag.remove_if([rect](const sf::RectangleShape val) {
if (rect.getPosition() == val.getPosition()) {
return true;
}
else {
return false ;
}
});
brainFrag -= 1;
collides = false;
}
}
if (brainFrag == 0) {
milo.x = oldPos.x;
milo.y = oldPos.y;
brainFrag = -1;
}

Answer 1

I don't understand your approach, you loop the rects, then when you find the one you want to remove, you search for it again through list<T>::remove_if.
I think that you forgot about the fact that you can use iterators in addition to a range-based loop:
for (auto it = brainFrag.begin(); it != brainFrag.end(); /* do nothing */)
{
bool collides = ...;
if (collides)
it = world1.level1.brainFrag.erase(it);
else
++it;
}
This allows you to remove the elements while iterating the collection because erase will take care of returning a valid iterator to the element next to the one you removed.
Or even better you could move everything up directly:
brainFrag.remove_if([&milo] (const auto& rect) {
return milo.sprite.getGlobalBounds().intersects(rect.getGlobalBounds())
}
A side note: there's no need to use an if statement to return a boolean condition, so you don't need
if (a.getPosition() == b.getPosition()
return true;
else
return false;
You can simply
return a.getPosition() == b.getPosition();