Hi guys new here need help on inherintance

[manbearbee]

Ok so I am in the procces of making a little yugioh game. For those who have never heard of it its a fairly popular or atleast it used to be back in the old days. I am having a little trouble on inherintance constructor thought yu guys could lend me a hand=). Heres the code I will comment the line that I get an error on.

#include <iostream>
#include <string>
using namespace std;


class MonsterCard{

protected:
	string Name;
	int AttackPoints;
	int DefencePoints;
	int StarLevel;


public:
	MonsterCard();
	MonsterCard(string names,int attkpoints,int defpoints, int strlvl);
	string getName();
	void setName(string names);
	int getAttackPoints();
	void setAttackPoints(int attkpoints);
	int getDefencePoints();
	void setDefencePoints(int defpoints);
	int getStarLevel();
	void setStarLevel(int starlvl);
	void attack(MonsterCard enemy);

};

class DarkMagician : public MonsterCard{
public:
	DarkMagician();

};


MonsterCard::MonsterCard(string names,int attkpoints,int defpoints, int strlvl){
	Name = names;
	AttackPoints = attkpoints;
	DefencePoints = defpoints;
	StarLevel = strlvl;
}
string MonsterCard::getName(){
	return Name;
}
int MonsterCard::getAttackPoints(){
	return AttackPoints;
}
int MonsterCard::getDefencePoints(){
	return DefencePoints;
}
int MonsterCard::getStarLevel(){
	return StarLevel;
}
void MonsterCard::setName(string names){
	Name = names;
}
void MonsterCard::setAttackPoints(int attkpoints){
	AttackPoints = attkpoints;
}
void MonsterCard::setDefencePoints(int defpoints){
	DefencePoints = defpoints;
}
void MonsterCard::setStarLevel(int strlvl){
	StarLevel = strlvl;
}
void MonsterCard::attack(MonsterCard enemy){
	int EnemyAttackPoints = enemy.getAttackPoints();
	string EnemyName = enemy.getName();

	cout << Name << " Has Attacked " << EnemyName << endl;

	if(AttackPoints > EnemyAttackPoints){
		cout << Name << " Has Destroyed Opponents " << EnemyName << endl;
	}else if(AttackPoints < EnemyAttackPoints){
		cout << EnemyName << " Has Destroyed Opponents" << Name << endl;
	}else if(AttackPoints == EnemyAttackPoints){
		cout << Name << " And Opponents " << EnemyName << " Have Been Destroyed"; 
	}


}
DarkMagician::DarkMagician(){
	MonsterCard("DarkMagician",2500,2000,7);
}

int main(){

	 DarkMagician dm = DarkMagician();
	 
	
	
	


	system("pause");
	return 0;
}

Here is the error I am getting on compiler.
main.obj : error LNK2019: unresolved external symbol "public: __thiscall MonsterCard::MonsterCard(void)" (??0MonsterCard@@QAE@XZ) referenced in function "public: __thiscall DarkMagician::DarkMagician(void)" (??0DarkMagician@@QAE@XZ)

[jim80y]

You've got a number of problems here; let's deal one at once.

1. Your error is saying that the linker can't find where you've defined the body of the MonsterCard::MonsterCard(void) function (the default constructor).

If you look through your code, you'll find it's right - you've declared it at line 16, but never defined it.

So, one solution would be to define it. Another would be to remove the declaration; then the compiler will provide you with a default version - for free!

However, the question remains - why is the default constructor being used at all? You're calling the constructor that takes string and int parameters.

2. Your DarkMagician::DarkMagician() constructor is slightly malformed (line 83).

What you should have done was to use what's called an initialiser list and called the base-class constructor in that.

DarkMagician::DarkMagician() : MonsterCard("DarkMagician", 2500, 2000, 7)
{
    // Any other initialisation can go here
}

As you wrote it, because you've not provided an implicitexplicit base-class call, the compiler is automatically calling the default base class constructor for you, which is MonsterCard(void), and as we know - there's no body defined for that function.

Also, by writing what you did for that constructor, what you've effectively done is to construct the DarkMagician as a default MonsterCard (line 83) and then line 84 creates a local-scope MonsterCard instance which is then destructed again when the function returns.

Hope that helps!

Cheers
Jim

[manbearbee]

Jim you are freaking awesome!
Thanks