c++ error C2662 cannot convert 'this' pointer from 'const Type' to 'Type &'

Question

I am trying to overload the c++ operator== but im getting some errors...

error C2662: 'CombatEvent::getType' : cannot convert 'this' pointer from 'const CombatEvent' to 'CombatEvent &'

this error is at this line

if (lhs.getType() == rhs.getType()) 

see the code bellow:

class CombatEvent {  public:     CombatEvent(void);     ~CombatEvent(void);      enum CombatEventType {         AttackingType,         ...         LowResourcesType     };      CombatEventType getType();     BaseAgent* getAgent();      friend bool operator<(const CombatEvent& lhs, const CombatEvent& rhs) {          if (lhs.getType() == rhs.getType())             return true;          return false;     }      friend bool operator==(const CombatEvent& lhs, const CombatEvent& rhs) {          if (lhs.getType() == rhs.getType())             return true;          return false;     }  private:      UnitType unitType; } 

can anybody help?

Answer 1

CombatEventType getType(); 

needs to be

CombatEventType getType() const; 

Your compiler is complaining because the function is being given a const object that you're trying to call a non-const function on. When a function gets a const object, all calls to it have to be const throughout the function (otherwise the compiler can't be sure that it hasn't been modified).

Answer 2

change the declaration to :

CombatEventType getType() const; 

you can only call 'const' members trough references to const.