calculator_controller.rb

class CalculatorController < ApplicationController
  before_action :set_first_number
  before_action :set_second_number, except: :square_root

  def addition
    result = @first_number + @second_number
    render json: result
  end

  def subtraction
    result = @first_number - @second_number
    render json: result
  end

  def multiplication
    result = @first_number * @second_number
    render json: result
  end

  def division
    result = @first_number / @second_number
    render json: result
  end

  def square_root
    render json: (@first_number.present? && @first_number > 0) ? @first_number**0.5 : 'must be > 0'
  end

  private
  def set_first_number
    @first_number = params[:n1].to_f if params[:n1].present?
  end

  def set_second_number
    @second_number = params[:n2].to_f if params[:n2].present?
  end
end