艰难地学习 Ruby #43

Question

谁能解释一下这里发生了什么？我知道这段代码很简单，但对我来说很难，我是终极初学者。我在这里被困了好几个小时，我无法弄清楚.. 当我运行代码时，CentralCorridor 类在我们有基本的 gets.chomp 提示的地方运行。该提示结束程序的所有答案（“射击！”，“闪避！”，“讲个笑话”）。我不知道如何进入其他场景（TheBridge 类、EscapePod 类、LaserWeaponArmory 类……）。我真的很想自己做这样的游戏，但我想不通.. 另外，如果有人可以向我解释这个 enter() 方法。 请帮忙 ：） 这是链接：http://ruby.learncodethehardway.org/book/ex43.html 或代码：

class Scene 
  def enter() # what this method do?
    exit(1)
  end
end

class Engine 

  def initialize(scene_map)
    @scene_map = scene_map
  end

  def play()
    current_scene = @scene_map.opening_scene()
    last_scene = @scene_map.next_scene('finished')

    while current_scene != last_scene
      next_scene_name = current_scene.enter()
      current_scene = @scene_map.next_scene(next_scene_name)
    end

    # be sure to print the last scene
    current_scene.enter()
  end
end

class Death < Scene

  @@quips = [
    "You died. You kinda suck at this",
     "Your mom would be proud...if she were smarter.",
     "Such a luser.",
     "I have a small puppy that's better at this."
  ]

  def enter()
    puts @@quips[rand(0..(@@quips.length - 1))] # 2. what is this?
    exit(1)
  end
end

class CentralCorridor < Scene

  def enter()
    puts "The Gothons of Planet Percal #25 have invaded your ship and destroyed"
    puts "your entire crew.  You are the last surviving member and your last"
    puts "mission is to get the neutron destruct bomb from the Weapons Armory,"
    puts "put it in the bridge, and blow the ship up after getting into an "
    puts "escape pod."
    puts "\n"
    puts "You're running down the central corridor to the Weapons Armory when"
    puts "a Gothon jumps out, red scaly skin, dark grimy teeth, and evil clown costume"
    puts "flowing around his hate filled body.  He's blocking the door to the"
    puts "Armory and about to pull a weapon to blast you."
    print "> "

    action = $stdin.gets.chomp

    if action == "shoot!"
      puts "Quick on the draw you yank out your blaster and fire it at the Gothon."
      puts "His clown costume is flowing and moving around his body, which throws"
      puts "off your aim.  Your laser hits his costume but misses him entirely.  This"
      puts "completely ruins his brand new costume his mother bought him, which"
      puts "makes him fly into an insane rage and blast you repeatedly in the face until"
      puts "you are dead.  Then he eats you."
      return 'death'

    elsif action == "dodge!"
      puts "Like a world class boxer you dodge, weave, slip and slide right"
      puts "as the Gothon's blaster cranks a laser past your head."
      puts "In the middle of your artful dodge your foot slips and you"
      puts "bang your head on the metal wall and pass out."
      puts "You wake up shortly after only to die as the Gothon stomps on"
      puts "your head and eats you."
      return 'death'

    elsif action == "tell a joke"
      puts "Lucky for you they made you learn Gothon insults in the academy."
      puts "You tell the one Gothon joke you know:"
      puts "Lbhe zbgure vf fb sng, jura fur fvgf nebhaq gur ubhfr, fur fvgf nebhaq gur ubhfr."
      puts "The Gothon stops, tries not to laugh, then busts out laughing and can't move."
      puts "While he's laughing you run up and shoot him square in the head"
      puts "putting him down, then jump through the Weapon Armory door."
      return 'finished'

    else
      puts "DOES NOT COMPUTE!"
      return 'central_corridor'
    end
  end
end

class LaserWeaponArmory < Scene

  def enter()
    puts "You do a dive roll into the Weapon Armory, crouch and scan the room"
    puts "for more Gothons that might be hiding.  It's dead quiet, too quiet."
    puts "You stand up and run to the far side of the room and find the"
    puts "neutron bomb in its container.  There's a keypad lock on the box"
    puts "and you need the code to get the bomb out.  If you get the code"
    puts "wrong 10 times then the lock closes forever and you can't"
    puts "get the bomb.  The code is 3 digits."
    code = "#{rand(1..9)}#{rand(1..9)}#{rand(1..9)}"
    print "[keypad]> "
    guess = $stdin.gets.chomp
    guesses = 0

    while guess != code && guesses < 10
      puts "BZZZZEDDD!"
      guesses += 1
      print "[keypad]> "
      guess = $stdin.gets.chomp
    end

    if guess == code
        puts "The container clicks open and the seal breaks, letting gas out."
        puts "You grab the neutron bomb and run as fast as you can to the"
        puts "bridge where you must place it in the right spot."
        return 'the_bridge'
    else
        puts "The lock buzzes one last time and then you hear a sickening"
        puts "melting sound as the mechanism is fused together."
        puts "You decide to sit there, and finally the Gothons blow up the"
        puts "ship from their ship and you die."
        return 'death'
    end
  end
end


class TheBridge < Scene

  def enter()
    puts "You burst onto the Bridge with the netron destruct bomb"
    puts "under your arm and surprise 5 Gothons who are trying to"
    puts "take control of the ship.  Each of them has an even uglier"
    puts "clown costume than the last.  They haven't pulled their"
    puts "weapons out yet, as they see the active bomb under your"
    puts "arm and don't want to set it off."
    print "> "

    action = $stdin.gets.chomp

    if action == "throw the bomb"
      puts "In a panic you throw the bomb at the group of Gothons"
      puts "and make a leap for the door.  Right as you drop it a"
      puts "Gothon shoots you right in the back killing you."
      puts "As you die you see another Gothon frantically try to disarm"
      puts "the bomb. You die knowing they will probably blow up when"
      puts "it goes off."
      return 'death'

    elsif action == "slowly place the bomb"
      puts "You point your blaster at the bomb under your arm"
      puts "and the Gothons put their hands up and start to sweat."
      puts "You inch backward to the door, open it, and then carefully"
      puts "place the bomb on the floor, pointing your blaster at it."
      puts "You then jump back through the door, punch the close button"
      puts "and blast the lock so the Gothons can't get out."
      puts "Now that the bomb is placed you run to the escape pod to"
      puts "get off this tin can."
      return 'escape_pod'
    else
      puts "DOES NOT COMPUTE!"
      return "the_bridge"
    end
  end
end


class EscapePod < Scene

  def enter()
    puts "You rush through the ship desperately trying to make it to"
    puts "the escape pod before the whole ship explodes.  It seems like"
    puts "hardly any Gothons are on the ship, so your run is clear of"
    puts "interference.  You get to the chamber with the escape pods, and"
    puts "now need to pick one to take.  Some of them could be damaged"
    puts "but you don't have time to look.  There's 5 pods, which one"
    puts "do you take?"

    good_pod = rand(1..5)
    print "[pod #]> "
    guess = $stdin.gets.chomp.to_i

    if guess != good_pod
      puts "You jump into pod %s and hit the eject button." % guess
      puts "The pod escapes out into the void of space, then"
      puts "implodes as the hull ruptures, crushing your body"
      puts "into jam jelly."
      return 'death'
    else
      puts "You jump into pod %s and hit the eject button." % guess
      puts "The pod easily slides out into space heading to"
      puts "the planet below.  As it flies to the planet, you look"
      puts "back and see your ship implode then explode like a"
      puts "bright star, taking out the Gothon ship at the same"
      puts "time.  You won!"


      return 'finished'
    end
  end
end

class Finished < Scene
  def enter()
    puts "You won! Good job."
  end
end

class Map
  @@scenes = {
    'central_corridor' => CentralCorridor.new(),
    'laser_weapon_armory' => LaserWeaponArmory.new(),
    'the_bridge' => TheBridge.new(),
    'escape_pod' => EscapePod.new(),
    'death' => Death.new(),
    'finished' => Finished.new(),
  }


  def initialize(start_scene)
    @start_scene = start_scene
  end


  def next_scene(scene_name)
    val = @@scenes[scene_name]
    return val
  end

  def opening_scene()
    return next_scene(@start_scene)
  end
end

a_map = Map.new('central_corridor')
a_game = Engine.new(a_map)
a_laser = EscapePod.new()
a_game.play()

Answer 1

亚历山大

你有一个包含许多组件的游戏：

引擎 - 游戏的主要入口点（你可以看出来，因为它有 play 方法） 你有一个 Map 对象，它只是可以在游戏中播放的不同场景的集合。每个场景都只是游戏中的另一个场景，都有自己的挑战。例如。在场景中，您在桥上；在另一个场景中，您在逃生舱中。在另一个你有武器什么的。

游戏中的所有场景都从 Scene 类继承它们的行为，如本例所示。

class EscapePod < Scene
#....
#Scene stuff
#...
end

上面的代码基本上说创建一个名为 EscapePod 的类，它可以做场景可以做的所有事情。

让你失望的是 Scene 类并没有做太多事情。它只有一个行为（这有点过于简化了），那就是它知道如何做一些叫做 enter 的事情，在这种情况下它会立即退出。这个 Scene 类是所有其他更有趣的场景的模板。

class Scene 
 def enter() # what this method do?
  exit(1)
 end
end

每个场景子类都会覆盖模板中的 enter 方法，以便在调用 enter 时做一些更有趣的事情，而不仅仅是退出。

下一个最简单的场景是 Finish 场景，它更有趣一点，它告诉你做得很好。

class Finished < Scene
  def enter()
  puts "You won! Good job."
 end
end

最后一件事。很明显，意图不是直接使用 Scene 类，而是仅使用必须覆盖 enter 方法的子类 EscapePod、Finish 等。

如果这是生产代码，您甚至可能会看到如下内容：

class Scene 
 def enter() # what this method do?
  raise "Scene 'enter' must not be used directly.Please subclass Scene and provide a meaningful    implementation for the 'enter' method" 
 end
end

我希望这会有所帮助。