Question

I’ve created this game thing in order to learn OOP and I’m having trouble with part of it. Here’s what’s causing me problems:

I have two classes. On line 3 of class Player, I have some code which is probably way wrong, but basically, what I’m trying to do is use armor to modify how much damage a player receives. I’m getting an error, though: “undefined method ‘protection’ for nil:NilClass (NoMethodError)

I have Armor as another class. I think the problem might relate to the fact that I am calling @armor.protection when protection is mentioned in Armor and @armor is mentioned in Player, but I am unsure how to fix this. I have added all the code I believe is relevant to my question below. Like I said, I’m really new at this, so please use terminology a noob could understand.

class Player
  def equip(armor)
    @armor = armor
  end

  def hit(damage)
    #damage = damage - @armor.protection
    @health -= damage
  end
end  

class Armor
  def initialize(name, protection)
    @protection = protection
  end
end

EDIT: added additional code to show all of what I’ve got going on for clarification. I don’t expect anyone to read all of what I’ve got, though. :S It’s probabably scary and snarled up. 😛

class Player 

  def initialize(name, health) 
    @name = name 
    @health = health 
  end 

  def equip(armor) 
    @armor = armor 
  end 

  def health 
    @health 
  end 

  def health=(value) 
    @health = value 
  end 

  def hit(damage) 
damage = damage - @armor.protection 
    @health -= damage 
  end 

  def dead? 
if @health <= 0 
return true 
elsif @health > 0 
return false 
end 
  end 

  def name 
    @name 
  end 

  def attack(target) 
    damage = rand(30) 
    puts "#{@name} attacks #{target.name}" 
target.hit(damage) 
puts "#{@name} hits #{target.name} for #{damage} damage." 
  end 
end 

class Armor 
  def initialize(name, protection) 
  @protection = protection 
  end 
end 


player1 = Player.new("Melanie", 100) 
player2 = Player.new("a Monster", 200) 
shirt = Armor.new('shirt', 4) 
player1.equip(shirt) 

while player1.dead? == false && player2.dead? == false 
  player1.attack(player2) 
    if player2.health > 0 
      puts "#{player2.name}'s health is at #{player2.health}." 
    elsif player2.health <= 0 
puts "#{player2.name} has no health." 
end 
  player2.attack(player1) 
    if player1.health > 0 
      puts "#{player1.name}'s health is at #{player1.health}." 
    elsif player1.health <= 0 
puts "#{player1.name} has no health." 
end 
end 

if player1.health > player2.health 
  puts "#{player2.name} is dead." 
  puts "#{player1.name} wins." 
elsif player2.health > player1.health 
  puts "#{player1.name} is dead." 
  puts "#{player2.name} wins." 
elsif player2.health == player1.health 
  puts "#{player1.name} and #{player2.name} killed each other." 
end 

Answer 1

If your Armor class has a protection method, it would work fine. However it doesn’t, so even if you were to call it from inside the Armor class, you’d get the same error. To define it you can either use attr_reader or attr_accessor or define it by hand.

class Armor
  attr_accessor :protection

  def initialize(name, protection)
    @protection = protection
  end
end

or

class Armor
  def initialize(name, protection)
    @protection = protection
  end

  def protection
    @protection
  end
end