I think I overridden the virtual method, but I still get: "X must implement the inherited pure virtual method Y"

Question

I am trying to implement an interface in C ++ for the game I am writing and I am running an error.

Here is the interface and its subclass that I created:

//Attack.h //defines a set of values associated with all attacks //and an interface for all attacks typedef unsigned const int attack_type; typedef unsigned const int p_attack_type; //defines the attack types static const attack_type NORMAL = 0; static const attack_type ADDER = 1; static const attack_type MULTIPLIER = 2; static const attack_type AREA_OF_EFFECT = 3; static const attack_type DAMAGE_OVER_TIME = 4; static const attack_type STATUS = 5; //String representation of the names of attack types static std::string attack_types [] = {"Normal","Adder","Multiplier","Area-Of-Effect","Damage-Over-Time","Status"}; class Attack { protected: std::string attack_name;//the name of this attack attack_type type;//the type of attack this represents int cool_down_turns;//represents the number of turns this ability cannot be used after being used bool causesGlobalCooldown;//does this attack cause ALL abilities to cooldown -- during combat should force cooldown on everything bool on_cool_down; public: Attack(std::string name, attack_type, int cooldown_t, bool causesGlobalCooldown = false) { this->attack_name = name; this->type = attack_type; this->causesGlobalCooldown = causesGlobalCooldown;//whether or not ALL abilities need to cooldown this->cool_down_turns = cooldown_t;//amount of turns that cooldown occurs this->on_cool_down = false;//whether or not this attack is on cooldown } //the main method called to perform this attack //calculate damage, calculate cooldown -- for spells calculate cost //return the amount of damage this attack does virtual int do_attack(int modifier, int roll) { //calculate damage int damage = calculate_damage(modifier,roll); //check cooldown if(this->cool_down_turns>0) { this->cooldown(true); } return damage; } //defined by sub classes -- useful to tell you how much damage the attack is going to do virtual int calculate_damage(int modifier, int roll) = 0; //**standard method definitions**// //get the attack name std::string get_attack_name() const { return this->attack_name; } //get the attack type attack_type get_attack_type() const { return this->type; } //get the attack type name of this attack std::string get_attack_type_name() const { return attack_types[this->type]; } //check the cooldown status of this attack bool cooldown() const { return on_cool_down; } //set the cooldown status of this attack void cooldown(bool set) { this->on_cool_down = set; } }; 

Here is the subclass:

 /* * Normal.cpp * * Created on: Jul 15, 2012 * Author: christian * Standard Definition of a Normal attack */ #include "Attack.h" class Normal : public Attack { public: Normal(std::string name) { Attack(name,NORMAL); } int calculate_damage(int modifier, int roll) const { return roll + modifier; } }; 

Error returned by the compiler: The type "Attack" must implement the inherited pure virtual method "Attack :: Store_Set"

Does anyone know the correct syntax for this? Do I have inheritance settings right?

Answer 1

const in your derrived class makes your signature on the derrive method of the class different from the virtual method in the base class. As for the compiler, you have overloaded calculate_damage in the Normal class, giving it a version of const and non-const .

Answer 2

You may be looking for

 Normal(std::string name) : Attack(name,NORMAL) {} 

This calls the base constructor, as you expected. The code, because it now creates a temporary unnamed variable of type Attack , which is an abstract class and its cause is an error.

In addition, the base function calculate_damage not const .