93 lines
2.7 KiB
Python
93 lines
2.7 KiB
Python
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import math
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import random
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import pygame
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from .doodles import Doodle
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class Line(Doodle):
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def __init__(self, parent=None):
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"""
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We keep the same interface as Doodle, to follow the Liskov substitution
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principle.
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We could add more *optional* arguments, but no more required ones
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than the parent class.
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"""
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super().__init__(parent)
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# a line is stored as a position (on the parent class)
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# and an offset vector
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self._offset_vec = (10, 0)
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def __repr__(self):
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return f"Line(pos={self.pos_vec}, end={self.end_vec}, {self._color})"
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def draw(self, screen):
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"""
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Implementation of the abstract draw function for the line.
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Note: This is a classic violation of single responsibility.
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Instead, you could imagine a class like:
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class DrawingBackend:
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def draw_doodle(doodle_type, doodle): ...
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class PygameBackend(DrawingBackend):
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def draw_line(...): ...
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This would make it possible to attach different
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drawing backends, restoring single-responsibility
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to the class and gaining flexibility from separating
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presentation logic from data manipulation.
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"""
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pygame.draw.aaline(screen, self._color, self.pos_vec, self.end_vec)
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def to(self, x: float, y: float) -> "Doodle":
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"""
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A setter for the line's offset vector.
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Example usage:
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Line().pos(10, 10).to(50, 50)
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Makes a line from (10, 10) to (50, 50).
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"""
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self._offset_vec = (x, y)
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return self
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def vec(self, degrees: float, magnitude: float):
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"""
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Alternate constructor, to create offset vector from angle & length.
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"""
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return self.to(
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magnitude * math.cos(math.radians(degrees)),
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magnitude * math.sin(math.radians(degrees)),
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)
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def random(self) -> "Doodle":
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"""
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Overrides the parent's random, by extending the behavior.
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This is an example of the open/closed principle.
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We aren't modifying the parent classes' random function
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since doing so would be fragile and break if the
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parent class added more options.
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Instead we just call it, and extend it with additional
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randomization.
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"""
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super().random()
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magnitude = random.random() * 100
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degrees = random.random() * 360
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return self.vec(degrees, magnitude)
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@property
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def end_vec(self):
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"""
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Parallel to pos_vec for end of line.
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"""
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return (
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self.x + self._offset_vec[0],
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self.y + self._offset_vec[1],
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)
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