operator overloading - 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).