In a previous post – On Class Structure – we discussed how to organize Ruby classes so that the logic is not buried in private methods, and instead is clear to readers what the class is responsible for doing. In this post, I want to expand on that a bit more and introduce result objects.

Let’s resume with our example:

class FindScore
  DEFAULT_SCORE = 0
  URL = 'http://example.com'.freeze

  def initialize(user, http_client = HTTParty)
    @user = user
    @http_client = http_client
  end

  def call
    make_api_request(@user, @http_client)
      .then { parse_response(_1) }
      .then { extract_score(_1) }
  end

  private

  def make_api_request(user, http_client = @http_client, url = URL)
    http_client.post(
      url,
      body: { user: user.id }
    )
  end

  def parse_response(response)
    JSON.parse(response.body)
  end

  def extract_score(response_body, default = DEFAULT_SCORE)
    response_body.fetch("score", default)
  end
end

That class doesn’t handle any errors. Each of the private methods can fail in different ways. For the sake of examples, lets say that we can encounter HTTP errors in make_api_request, the response may fail to be valid JSON or the response might have a different JSON shape than what we expect. One way to handle them is via exceptions or checking for specific conditions, and then ensuring that the value passed along is what the next step in our pipeline expects:

class FindScore
  DEFAULT_SCORE = 0
  URL = 'http://example.com'.freeze

  def initialize(user, http_client = HTTParty)
    @user = user
    @http_client = http_client
  end

  def call
    make_api_request(@user, @http_client)
      .then { parse_response(_1) }
      .then { extract_score(_1) }
  end

  private

  def make_api_request(user, http_client = @http_client, url = URL)
    response = http_client.post(
      url,
      body: { user: user.id }
    )

    response.ok? ? response.body : "{}"
  end

  def parse_response(response)
    JSON.parse(response.body)
  rescue JSON::ParserError
    {}
  end

  def extract_score(response_body, default = DEFAULT_SCORE)
    response_body.fetch("score", default)
  end
end

In that version, #make_api_request checks for a correct response, passing the response body to #parse_response. If the response is not successful however, it returns "{}", which is JSON that will be parsable by that response. In a similar manner, parsing JSON might raise JSON::ParseError. #parse_response rescues the exception, and returns a hash, as expected by #extract_score.

The code is now more resilient: It can handle some errors and recover from them by returning a value that can be used in the next method. However, these errors are being swallowed. What if we wanted to add some logging or metrics for each error, so we can understand our system better? One way, is to add a logging statement on the error branch of each method. I prefer another way, using result objects.

For our purposes a result object can either be a success or an error. In either case, it wraps another value, and it has some methods that act differently in each case. This object is known as a result monad, but let’s now dwell on that. Our result object will make it easier to write pipelines of method calls, without sacrificing error handling.

A very minimal implementation looks like this:

class Ok
  def initialize(value)
    @value = value
  end

  def and_then
    yield @value
  end

  def value_or(_other)
    @value
  end
end

class Error
  def initialize(error)
    @error = error
  end

  def and_then
    self
  end

  def value_or
    yield @error
  end
end

The polymorphic interface for Ok and Error has two methods: #and_then which is used to pipeline operations, and #value_or which is used to unwrap the value. Let’s see some examples:

Ok.new(1)
  .and_then { |n| Ok.new(n * 2) } # => 1 * 2 = 2
  .and_then { |n| Ok.new(n + 1) } # => 2 + 1 = 3
  .value_or(:error)
# => 3

Ok.new(1)
  .and_then { |n| Ok.new(n * 2) } # => 1 * 2 = 3
  .and_then { |n| Error.new("something went wrong") }
  .and_then { |n| Ok.new(n + 1) } # => Never called
  .and_then { |n| raise "Hell" } # => Never called either
  .value_or { :error }
# => :error

A chain of #and_then calls continue much like #then does, expecting a result object as a return value. However, if the return value at any point is an Error, subsequent blocks will not execute, and instead will continue returning the same result object. We then have a powerful way of constructing pipelines. Error handling can be left to the end.

Our class with error handling, can now be written as:

class FindScore
  DEFAULT_SCORE = 0
  URL = 'http://example.com'.freeze

  def initialize(user, http_client = HTTParty)
    @user = user
    @http_client = http_client
  end

  def call
    make_api_request(@user, @http_client)
      .and_then { parse_response(_1) }
      .and_then { extract_score(_1) }
      .value_or { |error_message|
        log.error "FindScore failed for #{@user}: #{error_message}"
        DEFAULT_SCORE
      }
  end

  private

  def make_api_request(user, http_client = @http_client, url = URL)
    response = http_client.post(
      url,
      body: { user: user.id }
    )

    response.ok? ? Ok.new(response.body) : Error.new("HTTP Status Code: #{response.status_code}")
  end

  def parse_response(body)
    Ok.new(JSON.parse(body))
  rescue JSON::ParserError => ex
    Error.new(ex.to_s)
  end

  def extract_score(parsed_json)
    score = parsed_json["score"]

    score.present? ? Ok.new(score) : Error.new("Score not found in response")
  end
end

Now, each method is responsible for returning either an Ok or and Error. The #call method is responsible for constructing the overall pipeline and handling the failure (i.e. returning a DEFAULT_SCORE), and with a single line, it also logs all errors.

This technique is quite powerful. The result objects are not limited to private class methods. Public methods can return them just as well. The Ok and Error implementation is quite minimal as a demonstration for this post. There are full-featured libraries out there (e.g. dry-rb), or you can roll your own pretty easily and expand the API to suit your needs (e.g. #ok?, #error?, #value!, #error, #fmap).

As I concluded in my previous post, writing Ruby classes so that the class is read in the same order as the operations will be performed leads to more legible code. Adding result objects enhances those same goals, and makes error conditions a first-class concern.

Tech Companies Are Irrational Pop Cultures

I agree with the author that there is a lot of Pop Culture in software companies, in the sense that they forget about the past, and there is a bias for “newer is better”. Thus, we get all the articles advising to choose “boring” technology with a proven track record.

There also does seem to be a good amount of contagion in the current round of layoffs. Companies are firing people, even if that they are doing well. I disagree that it is irrational. I dislike that characterization. It seems like a crutch for failing to understand the motivation for the people making the decisions. I believe that company executives do know that layoffs are bad for morale and create some problems down the line. There are some pretty smart people in company management. I think that they are making those decisions in spite of knowing that there are real downsides. Maybe the pressure from boards or investors is too much. Even if it is a case of copying what others are doing, it need not be irrational. There is an incentive to go with the flow: It’s safe. No one ever got fired for buying IBM. If things go wrong, you wont be blamed for making the same decision everyone else made.

Anti-Pattern: Iteratively Building a Collection

Mike Burns writes about how iteratively building a collection is an anti-pattern:

What follows are some lengthy method definitions followed by rewrites that are not only more concise but also more clear in their intentions.

It resonates with me that the pattern should be avoided. Brevity and clarity are great, but I think minimize mutation is a better reason to avoid building collections iteratively. Written in a functional style, your code handles less mutation of data structures, which means that it handles less state. Handling state is were a lot of complexity hides, and the source of many bugs. In fact, in Joe Armstrong’s estimation:

State is the root of all evil. In particular functions with side effects should be avoided.

The style of Ruby that the article encourages removes the state handling from your code. 👍🏻

[Is It Possible for My Internet Router to Wear Out?][routes]

Every few years, my routes start acting up in strange ways. Some devices function great, while others seem to have intermittent downloads. This articles confirms my suspicions. Router just wear out:

In general, routers can and do fail. The primary cause of failure for consumer grade equipment is heat stress. Most consumer grade hardware runs far too hot and have respectively poor air circulation compared to their ventilation needs.

To increase ventilation, I’ve started raising my router from the surface it’s on with a Lego structure that increases airflow from the bottom. It seems to improve heat dissipation by the imprecise measure of “it feels cooler to my touch”. 🤷🏻‍♂️

Recently DHH added Rubocop by default to Rails, and posted about his decision in a A writer’s Ruby blog post:

Some languages, like Go, have a built-in linter, which applies a universal style that’s been set by the language designers. That’s the most totalitarian approach. A decree on what a program should look like that’s barely two feet removed from a compile error. I don’t like that one bit.

It reminds me of Newspeak, the new INGSOC language from Orwell’s 1984. Not because of any sinister political undertones, but in the pursuit of a minimalist language, with no redundant terms or ambiguities or flair. Imagine every novel written in the same style, Hemingway indistinguishable from Dickens, Tolkien from Rowling. It would be awfully gray to enjoy the English language if there was only a single shade of prose.

The best code to me is indeed its own form of poetry, and style is an integral part of such expression. And in no language more so than Ruby.

There are probably people who would prefer the more conventional, literal style, and they could encode that preference in a lint rule. I’d have absolutely no problem with that, as long as they’re not trying to force me to abide by their stylistic preferences.

Now, in The Rails Doctrine DHH writes about Convention over Configuration:

One of the early productivity mottos of Rails went: “You’re not a beautiful and unique snowflake”. It postulated that by giving up vain individuality, you can leapfrog the toils of mundane decisions, and make faster progress in areas that really matter.

Who cares what format your database primary keys are described by? Does it really matter whether it’s “id”, “postId”, “posts_id”, or “pid”? Is this a decision that’s worthy of recurrent deliberation? No.

Let me try to unpack the two posts. Table names and primary and foreign key columns have strong conventions in Rails:

class Post < ApplicationRecord
  has_many :comments
end

class Comment < ApplicationRecor
  belongs_to :post
end

Implicit in the code above is that our database has a table posts with a primary key field id, and a table named comments with a primary key field id and a foreign key post_id referencing posts.id. There are many arguments to make about these specific conventions: About the plural table names, about using snake case, about the Ruby class names being singular, etc. The point over convention over configuration is that those changes don’t matter. The convention saves of from making unimportant decisions, in DHH words:

Part of the Rails’ mission is to swing its machete at the thick, and ever growing, jungle of recurring decisions that face developers creating information systems for the web. There are thousands of such decisions that just need to be made once, and if someone else can do it for you, all the better.

Let’s get back to Ruby syntax. The argument seems to be that the following two ways of writing the same code are different forms of self expression and the building blocks of poetry:

has_many :posts

has_many(:posts)

I am not convinced by that argument. I used to think that creating a style-guide for each team was a worthwhile exercise. Since then, I’ve been on 3 different teams in 12 years (hardly a lot by tech standards). I’ve come to experience the power of hitting the ground running on an unfamiliar Rails application, exactly because of convention over configuration. I’d rather we have more of that, with a convention for code style across teams.

In A writer’s Ruby, DHH says:

Imagine every novel written in the same style, Hemingway indistinguishable from Dickens, Tolkien from Rowling. It would be awfully gray to enjoy the English language if there was only a single shade of prose.

That would be an awful world indeed, but I don’t think it’s a fair comparison. Novels are mostly individual works of art. Code style is mostly a team endeavour with very different goals than literary works. Presumably, the team is working towards producing a maintainable code base that is easy to work on by current and future members of the team. Predictable style and idioms are better than poetic code. I would hate for all the novels I read to have the same style. I would hate just as much for the instructions on my dishwasher to be in the style of James Joyce or Leo Tolstoy.

For now, I am using standardrb, even if I don’t like all the conventions.

Rethinking Serverless with FLAME

Mind blown. This promises to be scalable and elastic with minimal code shenanigans. Like they mention: It doesn’t solve a problem. It removes it. Thanks to the power of the Erlang VM.

Everyday performance rules for Ruby on Rails developers

Overall, very good advice for Rails performance.

Ruby 3.3’s YJIT: Faster While Using Less Memory

Like having a cake and eating it too: Ruby got faster, and is using less memory. I’ve personally seen 20% improvement in speed building this blog

Per tradition, this Christmas a new version of ruby was released.

It promises performance improvements, especially with the YJIT turned on. Let’s see how it does using jekyll the static site generator for this very blog.

Before (ruby 3.2.2 without YJIT)

$ ruby -v
ruby 3.2.2 (2023-03-30 revision e51014f9c0) [arm64-darwin22]

$ jekyll build
Configuration file: /Users/ylansegal/Personal/blog/_config.yml
            Source: /Users/ylansegal/Personal/blog/src
       Destination: /Users/ylansegal/Personal/blog/_site
 Incremental build: disabled. Enable with --incremental
      Generating...
       Jekyll Feed: Generating feed for posts
                    done in 2.676 seconds.
 Auto-regeneration: disabled. Use --watch to enable.

$ jekyll build
[...]
                    done in 2.685 seconds.
$ jekyll build
[...]
                    done in 2.679 seconds.

Average: 2.68 seconds

After (ruby 3.3.0 with YJIT)

$ ruby -v
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]

$ jekyll build
Configuration file: /Users/ylansegal/Personal/blog/_config.yml
            Source: /Users/ylansegal/Personal/blog/src
       Destination: /Users/ylansegal/Personal/blog/_site
 Incremental build: disabled. Enable with --incremental
      Generating...
       Jekyll Feed: Generating feed for posts
                    done in 2.079 seconds.
 Auto-regeneration: disabled. Use --watch to enable.

$ jekyll build
[..]
                    done in 2.212 seconds.

$ jekyll build
[...]
                    done in 2.163 seconds.

Average: 2.15 seconds

Of course this is unscientific, but 20% local reduction in build time is impressive!