b.rb

class Client
  def initialize
    @all_entries = [*1..30].map { |i| "Hello this is #{i}" }
  end

  def get(option)
    from = option[:from_id] || 0
    @all_entries[from..(from + 5)]
  end
end

def get_all(client)
  result = []
  from_id = 0

  response = client.get(from_id: from_id)
  result.push *response

  until response.empty?
    from_id += response.count
    response = client.get(from_id: from_id)
    result.push *response
  end

  result
end

class PostEnumerator
  include Enumerable

  def initialize(client)
    @client = client
    @cursor = 0
  end

  def each(&block)
    response = @client.get(from_id: @cursor)

    return if response.empty?

    response.each &block
    @cursor += response.count
    each &block
  end
end

def get_all_refactored(client)
  PostEnumerator.new(client).to_a
end

client = Client.new
puts get_all(client)
puts get_all_refactored(client)
puts get_all(client) == get_all_refactored(client)