Started 14-6.

online_resources_site/docs/solutions/chapter_14.md

@@ -48,3 +48,11 @@ Make a set of buttons for *Alien Invasion* that allows the player to select an a
 The high score is reset every time a player closes and restarts *Alien Invasion*. Fix this by writing the high score to a file before calling `sys.exit()` and reading in the high score when initializing its value in `GameStats`.
 
 [Solution](https://github.com/ehmatthes/pcc_3e/tree/main/solution_files/chapter_14/ex_14_5_high_score)
+
+## 14-6: Refactoring
+
+Look for methods that are doing more than one task, and refactor them to organize your code and make it efficient. For example, move some of the code in `_check_bullet_alien_collisions()`, which starts a new level when the fleet of aliens has been destroyed, to a function called `start_new_level()`. Also, move the four separate method calls in the `__init__()` method in `Scoreboard` to a method called `prep_images()` to shorten `__init__()`. The `prep_images()` method could also help simplify `_check_play_button()` or `start_game()` if you’ve already refactored `_check_play_button()`.
+
+Note: Before attempting to refactor the project, see Appendix D to learn how to restore the project to a working state if you introduce bugs while refactoring.
+
+[Solution](https://github.com/ehmatthes/pcc_3e/tree/main/solution_files/chapter_14/ex_14_6_refactoring)

solution_files/chapter_14/ex_14_6_refactoring/alien.py

@@ -0,0 +1,34 @@
+import pygame
+from pygame.sprite import Sprite
+
+class Alien(Sprite):
+    """A class to represent a single alien in the fleet."""
+
+    def __init__(self, ai_game):
+        """Initialize the alien and set its starting position."""
+        super().__init__()
+        self.screen = ai_game.screen
+        self.settings = ai_game.settings
+
+        # Load the alien image and set its rect attribute.
+        self.image = pygame.image.load('images/alien.bmp')
+        self.rect = self.image.get_rect()
+
+        # Start each new alien near the top left of the screen.
+        self.rect.x = self.rect.width
+        self.rect.y = self.rect.height
+
+        # Store the alien's exact horizontal position.
+        self.x = float(self.rect.x)
+
+    def check_edges(self):
+        """Return True if alien is at edge of screen."""
+        screen_rect = self.screen.get_rect()
+        if self.rect.right >= screen_rect.right or self.rect.left <= 0:
+            return True
+
+    def update(self):
+        """Move the alien right or left."""
+        self.x += (self.settings.alien_speed *
+                        self.settings.fleet_direction)
+        self.rect.x = self.x

solution_files/chapter_14/ex_14_6_refactoring/alien_invasion.py

@@ -0,0 +1,284 @@
+import sys
+from time import sleep
+import json
+from pathlib import Path
+
+import pygame
+
+from settings import Settings
+from game_stats import GameStats
+from scoreboard import Scoreboard
+from button import Button
+from ship import Ship
+from bullet import Bullet
+from alien import Alien
+
+
+class AlienInvasion:
+    """Overall class to manage game assets and behavior."""
+
+    def __init__(self):
+        """Initialize the game, and create game resources."""
+        pygame.init()
+        self.clock = pygame.time.Clock()
+        self.settings = Settings()
+
+        self.screen = pygame.display.set_mode(
+                (self.settings.screen_width, self.settings.screen_height))
+        pygame.display.set_caption("Alien Invasion")
+
+        # Create an instance to store game statistics,
+        #   and create a scoreboard.
+        self.stats = GameStats(self)
+        self.sb = Scoreboard(self)
+
+        self.ship = Ship(self)
+        self.bullets = pygame.sprite.Group()
+        self.aliens = pygame.sprite.Group()
+
+        self._create_fleet()
+
+        # Make the Play button.
+        self.play_button = Button(self, "Play")
+
+        # Start game in an inactive state.
+        self.game_active = False
+
+    def run_game(self):
+        """Start the main loop for the game."""
+        while True:
+            self._check_events()
+
+            if self.game_active:
+                self.ship.update()
+                self._update_bullets()
+                self._update_aliens()
+
+            self._update_screen()
+            self.clock.tick(60)
+
+    def _check_events(self):
+        """Respond to keypresses and mouse events."""
+        for event in pygame.event.get():
+            if event.type == pygame.QUIT:
+                self._close_game()
+            elif event.type == pygame.KEYDOWN:
+                self._check_keydown_events(event)
+            elif event.type == pygame.KEYUP:
+                self._check_keyup_events(event)
+            elif event.type == pygame.MOUSEBUTTONDOWN:
+                mouse_pos = pygame.mouse.get_pos()
+                self._check_play_button(mouse_pos)
+
+    def _check_play_button(self, mouse_pos):
+        """Start a new game when the player clicks Play."""
+        button_clicked = self.play_button.rect.collidepoint(mouse_pos)
+        if button_clicked and not self.game_active:
+            self._start_game()
+
+    def _start_game(self):
+        """Start a new game."""
+        # Reset the game settings.
+        self.settings.initialize_dynamic_settings()
+
+        # Reset the game statistics.
+        self.stats.reset_stats()
+        self.game_active = True
+        self.sb.prep_score()
+        self.sb.prep_level()
+        self.sb.prep_ships()
+
+        # Get rid of any remaining aliens and bullets.
+        self.aliens.empty()
+        self.bullets.empty()
+
+        # Create a new fleet and center the ship.
+        self._create_fleet()
+        self.ship.center_ship()
+
+        # Hide the mouse cursor.
+        pygame.mouse.set_visible(False)
+
+    def _check_keydown_events(self, event):
+        """Respond to keypresses."""
+        if event.key == pygame.K_RIGHT:
+            self.ship.moving_right = True
+        elif event.key == pygame.K_LEFT:
+            self.ship.moving_left = True
+        elif event.key == pygame.K_q:
+            self._close_game()
+        elif event.key == pygame.K_SPACE:
+            self._fire_bullet()
+        elif event.key == pygame.K_p and not self.game_active:
+            self._start_game()
+
+    def _check_keyup_events(self, event):
+        """Respond to key releases."""
+        if event.key == pygame.K_RIGHT:
+            self.ship.moving_right = False
+        elif event.key == pygame.K_LEFT:
+            self.ship.moving_left = False
+
+    def _fire_bullet(self):
+        """Create a new bullet and add it to the bullets group."""
+        if len(self.bullets) < self.settings.bullets_allowed:
+            new_bullet = Bullet(self)
+            self.bullets.add(new_bullet)
+
+    def _update_bullets(self):
+        """Update position of bullets and get rid of old bullets."""
+        # Update bullet positions.
+        self.bullets.update()
+
+        # Get rid of bullets that have disappeared.
+        for bullet in self.bullets.copy():
+            if bullet.rect.bottom <= 0:
+                 self.bullets.remove(bullet)
+
+        self._check_bullet_alien_collisions()
+
+    def _check_bullet_alien_collisions(self):
+        """Respond to bullet-alien collisions."""
+        # Remove any bullets and aliens that have collided.
+        collisions = pygame.sprite.groupcollide(
+                self.bullets, self.aliens, True, True)
+
+        if collisions:
+            for aliens in collisions.values():
+                self.stats.score += self.settings.alien_points * len(aliens)
+            self.sb.prep_score()
+            self.sb.check_high_score()
+
+        if not self.aliens:
+            self._start_new_level()
+
+    def _start_new_level(self):
+        """Start a new level, after the fleet has been cleared."""
+        # Destroy existing bullets and create new fleet.
+        self.bullets.empty()
+        self._create_fleet()
+        self.settings.increase_speed()
+
+        # Increase level.
+        self.stats.level += 1
+        self.sb.prep_level()
+
+    def _update_aliens(self):
+        """
+        Check if the fleet is at an edge,
+          then update the positions of all aliens in the fleet.
+        """
+        self._check_fleet_edges()
+        self.aliens.update()
+
+        # Look for alien-ship collisions.
+        if pygame.sprite.spritecollideany(self.ship, self.aliens):
+            self._ship_hit()
+
+        # Look for aliens hitting the bottom of the screen.
+        self._check_aliens_bottom()
+
+    def _check_aliens_bottom(self):
+        """Check if any aliens have reached the bottom of the screen."""
+        screen_rect = self.screen.get_rect()
+        for alien in self.aliens.sprites():
+            if alien.rect.bottom >= screen_rect.bottom:
+                # Treat this the same as if the ship got hit.
+                self._ship_hit()
+                break
+
+    def _ship_hit(self):
+        """Respond to the ship being hit by an alien."""
+        if self.stats.ships_left > 0:
+            # Decrement ships_left, and update scoreboard.
+            self.stats.ships_left -= 1
+            self.sb.prep_ships()
+
+            # Get rid of any remaining aliens and bullets.
+            self.aliens.empty()
+            self.bullets.empty()
+
+            # Create a new fleet and center the ship.
+            self._create_fleet()
+            self.ship.center_ship()
+
+            # Pause.
+            sleep(0.5)
+        else:
+            self.game_active = False
+            pygame.mouse.set_visible(True)
+
+    def _create_fleet(self):
+        """Create the fleet of aliens."""
+        # Create an alien and find the number of aliens in a row.
+        # Spacing between each alien is equal to one alien width.
+        alien = Alien(self)
+        alien_width, alien_height = alien.rect.size
+        available_space_x = self.settings.screen_width - (2 * alien_width)
+        number_aliens_x = available_space_x // (2 * alien_width)
+
+        # Determine the number of rows of aliens that fit on the screen.
+        ship_height = self.ship.rect.height
+        available_space_y = (self.settings.screen_height -
+                                (3 * alien_height) - ship_height)
+        number_rows = available_space_y // (2 * alien_height)
+
+        # Create the full fleet of aliens.
+        for row_number in range(number_rows):
+            for alien_number in range(number_aliens_x):
+                self._create_alien(alien_number, row_number)
+
+    def _create_alien(self, alien_number, row_number):
+        """Create an alien and place it in the row."""
+        alien = Alien(self)
+        alien_width, alien_height = alien.rect.size
+        alien.x = alien_width + 2 * alien_width * alien_number
+        alien.rect.x = alien.x
+        alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
+        self.aliens.add(alien)
+
+    def _check_fleet_edges(self):
+        """Respond appropriately if any aliens have reached an edge."""
+        for alien in self.aliens.sprites():
+            if alien.check_edges():
+                self._change_fleet_direction()
+                break
+
+    def _change_fleet_direction(self):
+        """Drop the entire fleet and change the fleet's direction."""
+        for alien in self.aliens.sprites():
+            alien.rect.y += self.settings.fleet_drop_speed
+        self.settings.fleet_direction *= -1
+
+    def _update_screen(self):
+        """Update images on the screen, and flip to the new screen."""
+        self.screen.fill(self.settings.bg_color)
+        self.ship.blitme()
+        for bullet in self.bullets.sprites():
+            bullet.draw_bullet()
+        self.aliens.draw(self.screen)
+
+        # Draw the score information.
+        self.sb.show_score()
+
+        # Draw the play button if the game is inactive.
+        if not self.game_active:
+            self.play_button.draw_button()
+
+        pygame.display.flip()
+
+    def _close_game(self):
+        """Save high score and exit."""
+        saved_high_score = self.stats.get_saved_high_score()
+        if self.stats.high_score > saved_high_score:
+            path = Path('high_score.json')
+            contents = json.dumps(self.stats.high_score)
+            path.write_text(contents)
+
+        sys.exit()
+
+
+if __name__ == '__main__':
+    # Make a game instance, and run the game.
+    ai = AlienInvasion()
+    ai.run_game()

solution_files/chapter_14/ex_14_6_refactoring/bullet.py

@@ -0,0 +1,31 @@
+import pygame
+from pygame.sprite import Sprite
+
+class Bullet(Sprite):
+    """A class to manage bullets fired from the ship"""
+
+    def __init__(self, ai_game):
+        """Create a bullet object at the ship's current position."""
+        super().__init__()
+        self.screen = ai_game.screen
+        self.settings = ai_game.settings
+        self.color = self.settings.bullet_color
+
+        # Create a bullet rect at (0, 0) and then set correct position.
+        self.rect = pygame.Rect(0, 0, self.settings.bullet_width,
+            self.settings.bullet_height)
+        self.rect.midtop = ai_game.ship.rect.midtop
+
+        # Store the bullet's position as a decimal value.
+        self.y = float(self.rect.y)
+
+    def update(self):
+        """Move the bullet up the screen."""
+        # Update the decimal position of the bullet.
+        self.y -= self.settings.bullet_speed
+        # Update the rect position.
+        self.rect.y = self.y
+
+    def draw_bullet(self):
+        """Draw the bullet to the screen."""
+        pygame.draw.rect(self.screen, self.color, self.rect)

solution_files/chapter_14/ex_14_6_refactoring/button.py

@@ -0,0 +1,33 @@
+import pygame.font
+
+class Button:
+
+    def __init__(self, ai_game, msg):
+        """Initialize button attributes."""
+        self.screen = ai_game.screen
+        self.screen_rect = self.screen.get_rect()
+
+        # Set the dimensions and properties of the button.
+        self.width, self.height = 200, 50
+        self.button_color = (0, 135, 0)
+        self.text_color = (255, 255, 255)
+        self.font = pygame.font.SysFont(None, 48)
+
+        # Build the button's rect object and center it.
+        self.rect = pygame.Rect(0, 0, self.width, self.height)
+        self.rect.center = self.screen_rect.center
+
+        # The button message needs to be prepped only once.
+        self._prep_msg(msg)
+
+    def _prep_msg(self, msg):
+        """Turn msg into a rendered image and center text on the button."""
+        self.msg_image = self.font.render(msg, True, self.text_color,
+                self.button_color)
+        self.msg_image_rect = self.msg_image.get_rect()
+        self.msg_image_rect.center = self.rect.center
+
+    def draw_button(self):
+        # Draw blank button and then draw message.
+        self.screen.fill(self.button_color, self.rect)
+        self.screen.blit(self.msg_image, self.msg_image_rect)