Ruby: Unable to do math operations with two arguments

Question

Please bear in mind that I am fairly new to Ruby. I am currently following a tutorial that is asking me to create a basic calculator. I need to create a Calculator class, that has the following methods; description, add, subtract, multiply and divide.

My initialize method can successfully take two numbers, but I can't seem to get the other methods working.

Here is my code:

class Calculator
  attr_accessor :x, :y

  def self.description
    "Performs basic mathematical operations"
  end

  def initialize(x, y)
    @x = x
    @y = y
  end

  def add(x, y)
    x += y.to_i
  end

  def subtract(x, y)
    x -= y.to_i
  end
end    

I am getting "wrong number of arguments (0 for 2)"

Answer 1

The code is correct, but it doesn't make a lot of sense. You are passing the values to the initializer, therefore I expect your code to be used as it follows

c = Calculator.new(7, 8)
c.add
# => 15

and it's probably the way you are calling it. However, this is not possible because you defined add() to take two arguments. Therefore, you should use

c = Calculator.new(7, 8)
c.add(1, 2)
# => 3

But then, what's the point of passing x and y to the initializer? The correct implementation is either

class Calculator
  attr_accessor :x, :y

  def self.description
    "Performs basic mathematical operations"
  end

  def initialize(x, y)
    @x = x.to_i
    @y = y.to_i
  end

  def add
    x + y
  end

  def subtract
    x - y
  end
end  

or more likely

class Calculator
  def self.description
    "Performs basic mathematical operations"
  end

  def initialize
  end

  def add(x, y)
    x.to_i + y.to_i
  end

  def subtract(x, y)
    x.to_i - y.to_i
  end
end