Примеры задач с собеседования на позицию Middle Ruby разработчика

Question 1

Вариант ответа

Answer

			class Array
  def map
    return unless block_given?

    result = []
    i = 0

    while self[i] do
      result << yield(self[i])
      i += 1
    end

    result
  end
end

Проверка использования: [1,2,3,4].map { |x| x * 10 }

Question 2

Вариант ответа

Answer

			module AttrAccessor
  def self.included(klass)
    klass.extend(ClassMethods)
  end

  module ClassMethods
    def custom_attr_accessor(*args)
      args.each do |arg|
        define_method(arg) do
          self.instance_variable_get("@#{arg}")
        end

        define_method("#{arg}=") do |value|
          self.instance_variable_set("@#{arg}", value)
        end
      end
    end
  end
end

Проверка использования:

			class Car
  include AttrAccessor
  custom_attr_accessor :wheels_count, :driver_name
end

car = Car.new
car.wheels_count = 4
p car.wheels_count

car.driver_name = 'Kevin'
p car.driver_name

Question 3

Вариант ответа

Answer

			class Text
  def initialize(body, formatter)
    @body = body
    @formatter = formatter
  end

  def formatted
    @formatter.render(@body)
  end
end

class BaseFormatter
  def render(text)
    raise 'Not implemented :render method'
  end
end

class HtmlFormatter < BaseFormatter
  def render(text)
    "#{text}"
  end
end

class JsonFormatter < BaseFormatter
  def render(text)
    "{ body: #{text} }"
  end
end

class XmlFormatter < BaseFormatter
end

Проверка использования:

			text = Text.new('Text', JsonFormatter.new)
puts text.formatted

Question 4

Вариант ответа

Answer

			class Fixnum
  def to_proc
    Proc.new { |item| item % self == 0 }
  end
end

Question 5

Вариант ответа

Answer

			require 'logger'

module Forceable
  def method_missing(method, *args, &block)
    if method =~ /force_(\w+)/ && previous_value = self.instance_variable_get("@#{$1}")
      self.instance_variable_set("@#{$1}", args.first)

      puts "Post changes #{$1} value from #{previous_value} to #{args.first}"
    else
      super
    end
  end
end

Post.include(Forceable)

Проверка использования:

			post = Post.new('Title', 'Body')
post.publish!
p post.state
post.publish!
p post.state
post.force_state(:draft)
p post.state