---
created: 2026-04-16 08:01
course: "[[29605397 - OOP]]"
topic: classes
related:
type: lecture
status: 🔴
tags:
  - university
  - cpp
---
## 📌 Summary

> [!abstract]
> Introduction of Classes and visibility modifiers
> 

---

## 📝 Content

C approach of defining a Pokemon:
```C
typedef struct {
	int exp;
	int level;
	int attack;
	int defense;
	int speed;
	int hp;
} Pokemon;

void upgrade(*Pokemon p, int gainedExp) {
	p->exp += gainedExp;
	if (p->exp >= 4000) {
		p->exp -= 4000;
		p->level += 1;	
	}
}

int main() {
	Pokemon fukano = {3600, 1, 400, 400, 20, 1200};
	printf("Exp of fukano: %d", fukano);
	upgrade(&fukano, 400);
	printf("Exp of fukano: %d", fukano);
	return 0;
}
```

In C++ we use classes:
```C++
class Pokemon {
public: // visibility modifier
	int exp;
	int level;
	int hp;

	void upgrade(int gainedExp) {
		exp += gainedExp;
		if (exp >= 4000) {
			exp -= 4000;
			level += 1;	
		}
	}
}

int main() {
	Pokemon fukano = {3600, 1, 1200};
	cout << "Exp of fukano: " << fukano.exp << endl;
	fukano.upgrade(400);
	cout << "Exp of fukano: " << fukano.exp << endl;
}
```

### Scope Modifiers
If we want to hide data beyond the class itself we can use the `private` visibility modifier:

```C++
class Pokemon {
public:
	string name;
	
private: 
	int exp;
	int level;
	int hp;

public:
	void upgrade(int gainedExp) {
		exp += gainedExp;
		if (exp >= 4000) {
			exp -= 4000;
			level += 1;	
		}
	}
}

int main() {
	Pokemon fukano = {3600, 1, 1200};
	fukano.upgrade(400); // this is OK
	fukano.exp += 400; // this is not OK
}
``` 

### Getters and Setters
_Getters and Setters_ allow **controlling the change** like:
- ensuring a number is in a range
- update depending parameters (like level with exp)

```c++
class Pokemon {
// ...
public:
	void setExp() { /*...*/ }
	int getExp() { /*...*/ }
}
```

### Constructors

Given the class:
```C++
class Pokemon {
private:
	int exp;
	int level;
}
```

We can create a new instance using the _basic constructor_:
```C++
class Pokemon {
// ...
public: 
	// Default constructor: allows Pokemon <name>; -> exp = 0, level = 0;
	Pokemon(): exp(0), level(0) {}; 
	// or
	Pokemon(0, 0);

	// Base constructor
	Pokemon(int e, int l) {
		exp = e;
		level = l;		
	}
	// or as
	Pokemon(int e, int l): exp(e), level(l) {};
}

int main() {
	Pokemon fukano(3600, 1);
}
```

We can also create an instance as a copy of another object of the _same class_:
```C++
class Pokemon {
// ...
public:
	Pokemon(const Pokemon& other): exp(other.exp), level(other.level) {}
}
```