515 lines
9.3 KiB
Markdown
515 lines
9.3 KiB
Markdown
---
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marp: true
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paginate: true
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class: invert
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# theme: uncover
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footer: Tutorium 09 - 16.12.2023 - Nils Pukropp - https://s.narl.io/s/tutorium-09
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header:
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---
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# Tutorium 09
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Korrektur 08 - Vererbung, OOP, Datenkapselung
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---
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# Korrektur 08
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---
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# Punkteverteilung
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---
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# Häufige Fehler
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* `@dataclass` nicht verwendet
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* `__init__` überschrieben, obwohl `@dataclass` das macht und dann `super().__init__()` vergessen
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* Kein Polymorphismus verwendet, also Code Duplikate oder auf `self` gematched/`isinstance()` verwendet
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* Code nicht getestet, Datei nicht ausführbar => **0 Punkte**!
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---
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# Musterlösung - Aufgabe 8 a,b)
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```py
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import math
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from dataclasses import dataclass
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@dataclass
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class Vec2:
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x: float
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y: float
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def abs(self) -> float:
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return math.sqrt(self.x * self.x + self.y * self.y)
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```
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---
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# Musterlösung - Aufgabe 8 c)
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```py
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@dataclass
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class GameObject:
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position: Vec2
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radius: int
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alive: bool
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color: tuple[int, int, int]
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@dataclass
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class Projectile(GameObject):
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speed: float
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@dataclass
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class StaticObject(GameObject):
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rotation: float
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```
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---
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# Musterlösung - Aufgabe 8 c)
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```py
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class Item(StaticObject):
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amount: int
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class Ammunition(Item):
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pass
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class Health(Item):
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pass
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class Ship(GameObject):
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shots: int
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hp: int
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class Asteroid(StaticObject):
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special: bool
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```
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---
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# Musterlösung - Aufgabe 8 d)
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```python
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class GameObject:
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# ...
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def update(self, width: int, height: int, delta: float):
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if not (0 <= self.position.x < width and 0 <= self.position.y < height):
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self.alive = False
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class Projectile(GameObject):
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speed: float
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def update(self, width: int, height: int, delta: float):
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self.position.y -= delta * self.speed
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super().update(width, height, delta)
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```
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---
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# Musterlösung - Aufgabe 8 d)
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```python
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class StaticObject(GameObject):
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rotation: float
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def update(self, width: int, height: int, delta: float):
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self.position.y += delta
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self.rotation += delta / self.radius
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super().update(width, height, delta)
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class Ship(GameObject):
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shots: int
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hp: int
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def update(self, width: int, height: int, delta: float):
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if self.hp <= 0:
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self.hp = 0
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self.alive = False
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super().update(width, height, delta)
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```
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---
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# Musterlösung - Aufgabe 8 e)
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```python
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@dataclass
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class GameObject:
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# ...
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def is_colliding(self, other: "GameObject") -> bool:
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dist = Vec2(self.position.x - other.position.x, self.position.y - other.position.y)
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return dist.abs() <= self.radius + other.radius
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```
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---
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# Musterlösung - Aufgabe 8 f)
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```python
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class GameObject:
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# ...
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def on_collision(self, other: "GameObject"):
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pass
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class Projectile(GameObject):
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# ...
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def on_collision(self, other: 'GameObject'):
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if not isinstance(other, Ship):
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self.alive = False
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```
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---
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# Musterlösung - Aufgabe 8 f)
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```python
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class StaticObject(GameObject):
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# ...
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def on_collision(self, other: 'GameObject'):
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self.alive = False
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class Ship(GameObject):
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# ...
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def on_collision(self, other: 'GameObject'):
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match other:
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case Asteroid():
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self.hp -= other.radius
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case Health():
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self.hp += other.amount
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case Ammunition():
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self.shots += other.amount
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```
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---
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# Musterlösung - Aufgabe 8 f)
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```python
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@dataclass
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class Asteroid(StaticObject):
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special: bool
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def on_collision(self, other: 'GameObject'):
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if not isinstance(other, Asteroid):
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self.alive = False
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```
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---
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# Musterlösung - Aufgabe 8 g)
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```python
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@dataclass
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class Ship(GameObject):
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# ...
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def shoot(self) -> Projectile:
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alive = False
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if self.shots:
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self.shots -= 1
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alive = True
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pos = Vec2(self.position.x, self.position.y)
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return Projectile(pos, 5, alive, (255, 0, 0), 3)
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```
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---
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# Musterlösung - Aufgabe 8 h)
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```python
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@dataclass
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class GameObject:
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# ...
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def draw(self, screen: pygame.Surface):
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pygame.draw.circle(screen, self.color, (self.position.x, self.position.y), self.radius)
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```
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---
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# Override-Dekorator
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- ist in `typing`
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- Wird über Methoden geschrieben, die überschrieben werden
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- Pylance zeigt einen Fehler an, wenn die überschriebene Methode in keiner Oberklasse gefunden wird
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- Hilft Fehler vorzubeugen - falsche Signatur, Parameter, ...
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---
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# Override-Dekorator - Beispiel
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```python
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from typing import override
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from dataclasses import dataclass
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@dataclass
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class GameObject:
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def on_collision(self, other: 'GameObject'):
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pass
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class StaticObject(GameObject):
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@override
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def on_collisoin(self, other: 'GameObject'): # Pylance-Error
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self.alive = False
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```
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---
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# Override-Dekorator - Beispiel
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```python
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from typing import override
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from dataclasses import dataclass
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@dataclass
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class GameObject:
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def on_collision(self, other: 'GameObject'):
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pass
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class StaticObject(GameObject):
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@override
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def on_collision(self): # Pylance-Error
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self.alive = False
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```
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---
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# Datenkapselung
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- Man möchte manche Implementierung verstecken
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- Wenn andere deinen Code verwenden, dann möchte man eine Schnittstelle anbieten die intuitiv ist.
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```python
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@dataclass
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class MyList[T]:
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internal_list: list[T] = []
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def add(self, item: T) -> None:
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self.internal_list += [other]
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```
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---
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# Datenkapselung - warum ist das schlecht?
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```python
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from my_collections import MyList
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xs = MyList()
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xs.internal_list # ????
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```
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- was sollen wir mit `internal_list`?
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- andere sollten nur auf `add()` zugreifen können
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---
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# Private Attribute
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```python
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@dataclass
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class MyList[T]:
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_internal_list: InitVar[list[T]]
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_length: InitVar[int]
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def __init__(self):
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self.__internal_list = []
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self.__length = 0
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def add(self, item: T):
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self.__internal_list += [item]
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self.__length += 1
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@property
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def length(self) -> int:
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return self.__length
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```
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---
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# Private Attribute
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```python
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@dataclass
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class MyList[T]:
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_internal_list: InitVar[list[T]]
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_length: InitVar[int]
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def __init__(self):
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self.__internal_list = []
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self.__length = 0
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```
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---
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# Private Attribute
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```python
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@dataclass
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class MyList[T]:
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_internal_list: InitVar[list[T]]
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_length: InitVar[int]
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def __init__(self):
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self.__internal_list = []
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self.__length = 0
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def add(self, item: T):
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self.__internal_list += [item]
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self.__length += 1
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@property
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def length(self) -> int:
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return self.__length
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```
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---
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# Private Attribute - Setter
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- Manchmal wollen wir trotzdem private Attribute setzen
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- Aber vielleicht nur wenn bestimmte Bedingungen erfüllt sind
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```python
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class GameObject:
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_position: InitVar[tuple[int, int]]
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def __post__init__(self, position: tuple[int, int]):
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assert (0, 0) <= position
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self.__position = position
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@property
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def position(self) -> tuple[int, int]:
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return self.__position
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```
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---
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# Private Attribute - Setter
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```python
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@dataclass
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class GameObject:
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_position: InitVar[tuple[int, int]]
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def __post_init__(self, position: tuple[int, int]):
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assert (0, 0) > position
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self.__position = position
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@property
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def position(self) -> tuple[int, int]:
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return self.__position
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@position.setter
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def position(self, position: tuple[int, int]):
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if (0, 0) > position:
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return
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self.__position = position
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```
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---
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# Comprehensive-Guide to `class`
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## `@dataclass`
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- Attribute werden im Klassenrumpf definiert
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- können mit einem Standardwert definiert werden
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- `__init__`, `__post_init__`, `__repr__`, `__eq__`, `__lt__`, `__le__`, `__gt__`, `__ge__`, ... werden automatisch generiert
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- In der Vorlesung benutzen wir nur `dataclass`
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---
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# Comprehensive-Guide to `class`
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## `@dataclass`
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- Attribute die im Klassenrumpf definiert werden, werden automatisch in die `__init__` generiert, auch wenn es einen Standardwert gibt!
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```python
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@dataclass
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class A:
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x: int
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y: int = 0
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def __init__(self, x: int, y: int = 0): # das macht @dataclass von selber!
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self.x = x
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self.y = y
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```
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---
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# Comprehensive-Guide to `class`
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## `Enum`
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- Wenn man eine endliche Aufzählung braucht (endliche Menge)
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- macht die Fallunterscheidung einfach weil es endliche Elemente gibt
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- Versichert auch dass kein quatsch übergeben wird wie zb bei `str`
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- **niemals** mit `@dataclass`, sonst geht alles kaputt
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---
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# Enum - Beispiel
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```python
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def eval[T: (int | float)](operator: str, x: T, y: T) -> T:
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match operator:
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case '+':
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return x + y
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case '-':
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return x - y
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case '*':
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return x * y
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case '/' if y != 0:
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return x / y
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case _:
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return 0
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```
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---
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# Enum - Beispiel
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```python
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from enum import Enum, auto
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class Op(Enum):
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ADD = auto()
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SUB = auto()
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DIV = auto()
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MUL = auto()
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```
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Jetzt passen wir die Methodensignatur an
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```python
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def eval[T: (int | float)](operator: Op, x: T, y: T) -> T:
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```
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Jetzt kann nichts beliebiges als `operator` übergeben werden
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---
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# Blatt 09 - Fragen?
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- Abgabe: 18.12. - 09:00
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- Testet euren Code!
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- Es gibt keine dummen Fragen wenns ums Verständnis geht
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