Object has type qualifiers that are not compatible with the member function

Question

My class Game has a member EntityManager entityManager_.

The class EntityManager has a private member Player player_ and the public getter function Player &EntityManager::getPlayer() which returns player_.

The class Player has for example the functions void startMoving() and sf::Vector2f getPosition() const.

Now, I can without problems call entityManager_.getPlayer().startMoving(); from within my Game class, but when I try for example the following code to get the player's position:

sf::Vector2f playerPosition = entityManager_.getPlayer().getPosition();

I get the following error:

IntelliSense:

EntityManager Game::entityManager_

Error: the object has type qualifiers that are not compatible with the member function

object type is: const EntityManager

Output:

game.cpp(261): error C2662: 'EntityManager::getPlayer' : cannot convert 'this' pointer from 'const EntityManager' to 'EntityManager &'
          Conversion loses qualifiers

I tried removing the const from the player's getPosition function but nothing changed.

I know it probably has something to do with the const but I can't figure out what to change! Could someone please help me?

I suspect you don't have a const version of getPlayer but you have not shown any code. — Neil Kirk, Jul 10 '14 at 12:52
Adding `const` to `getPlayer` removes the error, but could you tell me what I have to return then instead of `player_`? Because now `getPlayer` tells me: error: qualifiers dropped in reference of type "Player &" to initializer of type "const Player" — A. D., Jul 10 '14 at 12:55
@A.D.: Are you inside a member function that is itself declared `const`? — David Rodríguez - dribeas, Jul 10 '14 at 13:00
@DavidRodríguez-dribeas Ah, yes. That member function is indeed `const`. I removed it and now it's working! Thank you — A. D., Jul 10 '14 at 13:05
You need `Player &EntityManager::getPlayer() { return _player; }` AND `const Player &EntityManager::getPlayer() const { return _player; }` — Neil Kirk, Jul 10 '14 at 13:06

score 21 · Accepted Answer · answered Jul 10 '14 at 13:00

The error message is quite explicit:

game.cpp(261): error C2662: 'EntityManager::getPlayer' : 
               cannot convert 'this' pointer from 'const EntityManager' to 
                                                  'EntityManager &'
          Conversion loses qualifiers

In the context where you are calling getPlayer the object/reference is const. You cannot call a non-const member function on a const object or through a const reference or pointer to const.

Because the error refers to this, the most likely reason is that this code is inside a member function that is const.

Object has type qualifiers that are not compatible with the member function

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