Friendly attributes pattern in Ruby
brunosutic.com
brunosutic.com
I once was hackathoning with a colleague who was trying to get me excited about Rails, and he said, "look how great this is -- if you want the idea of '1 day', you can just write `1.day`!". I opened up a irb to try it out, and it didn't work. We were both confused for a bit until he figured out that it was a Rails thing, not a Ruby thing. That Rails globally punches date/time methods into integers, which he thought was cool, and I thought was abhorrent. I asked, "okay, if I came across this code, how would I be able to know that it came from Rails?" He said, there wasn't any way to really trace a method to its source definition, you just kinda have to know, and I decided this whole thing was too much of a conflict with my mental model for how humans and code and computers should work together.
Look, I'm not a big fan of all of Rails' monkeypatching. That's why I don't use Rails anymore, I use other Ruby frameworks like Bridgetown, Roda, and Hanami. But there's definitely a way to dive into the "magic" and find out what's going on.
Even if you can see the source, it still seems difficult to understand where the monkeypatch came from if you have transitive dependencies and whatnot.
That way, it's easy to trace, forwards (from package to all the methods it introduces) & backwards (from method to package), who introduced a method, where, and why.
Other than that, I think a lot of this aversion to "ruby magic" is a bit overblown. The ability to cleanly remold any part of the system with minimal friction, to suit the app you're building right now - that's a KEY part of what makes it special.
Its like all these polemics warning wannabe lispers away from using macros. Lisp, Smalltalk, and ruby, all give you very powerful shotguns to express your creative ideas. If you can't stop blowing your own foot off, then pick a different language with a different paradigm.
> That way, it's easy to trace, forwards (from package to all the methods it introduces) & backwards (from method to package), who introduced a method, where, and why.
Doesn't Method#source_location in Ruby provide a mechanism for this?
Though, in modern (>3.x) Ruby, its probably better to avoid monkey-patching unless you need to override behavior exposed to consumers that aren't opting in, and just use Refinements that consumers can opt-in to using.
I can. It is, of course, those who worked on the project before me, that expressed their all-too-human over-confidence in their own abilities and judgement.
And then we would spend-a-weekend to rip-out the changes they'd made to Smalltalk system classes, that conflicted with the version upgrade.
(Something about the narcissism of small differences.)
plans = {
1.month => {standard: 10, pro: 50, enterprise: 100},
1.year => {standard: 100, pro: 500, enterprise: 1000}
}
plans.each do |interval, details|
details.each do |name, amount|
Billing::Plan::Factory.find_or_create_by!(name: , interval:, amount:)
end
endAlso ActiveSupport has Object#with_options which has a similar intent, but I rarely ever see it used in codebases.
This way of handling attributes is monumentally less efficient than just using keyword attributes, which are optimized by the runtime.
Unfortunately you’ll find this is every Ruby code base: tiny readability improvements that are performing allocations and wasting cycles for no real reason other than looking better.
I’ve certainly done that and it’s expected, efficient code looks “weird”. A regular “each” loop that looks complicated will be transformed into multiple array method chaining, allocating the same array many times. If you don’t do it someone else will.
Let's take this example from the article:
Billing::Plan.find_or_create_all_by_attrs!(
1.month => {standard: 10, pro: 50, enterprise: 100},
1.year => {standard: 100, pro: 500, enterprise: 1000}
)
The problem with that logic is that it’s pervasive: people have that same attitude everywhere even if no IO is being done. That’s how we get multi gigabyte processes.
The whole language (and Rails) also pushes you towards a less efficient path. For instance you’re probably iterating over those six plans and inserting them individually in the DB. Another approach would’ve been to accumulate all of them in memory then build and perform a single query. That’s not something people really consider because it’s “micro” optimization and makes the code look worse. But if you miss out on hundreds of these micro optimizations then you get a worse system.
In a general sense optimizing Ruby is indeed futile: any optimization is dwarfed by just choosing a different language.
I say all this as someone who has worked with it for two decades, I like the language, it’s just laughably inefficient.
And the question is always “fast enough for what?” Different languages are more suitable for different types of projects. I wouldn’t code a rendering engine in Ruby but for web apps it’s amazing.
Those optimizations to the VM are just very workload specific and become less relevant today when you’re using containers and fractional CPU/mem. It also doesn’t take much for a dev to write the wrong code and make them irrelevant again. Even if you get everything right you’re leaving so much performance on the table it feels like crumbs.
For small web apps Rails is fine though. I just never worked on one. The issue is perhaps no one threw the code away when it got big.
Rails apps can get very expensive server wise because the “IO is slow anyways” attitude means more servers will be needed to serve the same amount of requests. For a specific bad case I worked at, the cloud bill was the same cost of 15 senior developers. And it was an app without external users (I was actually responsible for the external parts of it, it was isolated and not in Rails).
Excessive abstraction at the ORM can also make it extremely difficult to optimize db queries, so each user request can trigger way more DB queries than necessary, and this will require more db power. I have seen this happening over and over due to abstraction layers such as Trailblazer, but anything that is too layered clean-code style will cause issues and requires constant observation. And refactoring is made difficult due to “magic”. Even LLMs might find it too much.
Another problem with the slowness is that it slows down local development too. The biggest test suite I ever saw took 2 hours to run in a 60-machine cluster, so 120 hours of CI. Impossible to run locally, so major refactoring was borderline impossible without a huge feedback cycle.
The solution for the slow development ends up being hiring more developers, of course, with each one responsible for a smaller part of the app. In other companies these kind of features I saw would be written by people over days, not by team over months.
The terseness of both Ruby and Rails is also IMO countered by the culture of turning 10-line methods into bigger classes and using methods and instance variables instead of local variables. So it also hurts both readability (because now you have 5x more lines than needed) but also hurts optimization and stresses the garbage collection. If you know this, you know. I have seen this in code from North+Latin American, European and Japanese companies, so it’s not isolated cases. If you don’t know I can provide examples.
I have seen this happening with other tech too, of course, but with Rails it happens much much faster IME.
It is also 100% preventable, of course, however a lot of advice on how to prevent these problems will clash with Ruby/Rails traditions and culture.
These are just examples out of personal experience, but definitely not isolated cases IMO.
Static typing would be the main thing teams would've been better off with. I was big on dynamic languages, love Clojure/LISPs and still work with Ruby and JS today, but you just can't trust 100 developers with it. Last company I worked for I ran the dev team and did some bug analysis: conservatively 60% of bugs were things a simple static type system would've caught.
Very few business logic bugs. We had loads of tests but these simple bugs still popped up. Someone in team A would change a method's return type, find and replace in the codebase, but miss some obscure case from team D. Rinse and repeat. Nothing complicated, just discipline but you can't trust discipline on a 500k LoC codebase and a language with no guardrails.
Performance would've been the other main advantage of static typing. While most people think their Rails app will be IO-bound forever that's really downplaying their product. In actuality every company that mildly succeeds will start to acquire CPU-bound workloads and it'll come a point where they are the bottleneck. One might argue that it is at this point you ditch Ruby but in reality no one really wants to run a polyglot company: it's hard to hire, hard to fill in gaps, hard to manage and evaluate talent.
People underestimate the impact of performance on the bottom line these days with phrases like "memory is cheap; devs are not". Like the sibling commenter put it the monthly cloud bill on that last company would've paid about 20 dev salaries. Most of that was for the app servers. That for an app that served about 500 req/sec at peak. You can imagine the unnecessary pressure that puts on the company's finances.
Better choices would've been Go, Rust, even something on the JVM.
About performance, not sure how you think static typing could solve it, but considering the significant investment recently in JITs, in particular YJIT and ZJIT, again, the big apps seem to agree with you and have done something about it?
Even if you ditch CRuby for the JVM, you can still use JRuby, and still leverage the language while not being pulled down by the runtime.
It's not like you're without options.
The thing about "it's IO bound anyway so who cares" is that it forces you to scale the app much earlier.
At a company I worked, a single Golang instance (there was backup) was able to handle every single request by itself during peak hours, and do authentication, partial authorization, request enrichment, fraud detection, rate limiting and routing to the appropriate microservice. I'm not saying it was a good idea to have a custom Ingress/Proxy app but it's what we had.
By contrast, the mesh of Rails applications required a few hundred machines during peak time to serve the same number of requests, and none of it was CPU-heavy. It was DB heavy!
If it had been a Golang or JVM or Rust app it would require a much smaller fleet to serve.
This same pitfall exists in every language. This has nothing to do with Ruby.
And after a couple years even Postgres is struggling because the amount of queries is too massive because of abstractions that don’t lend themselves to optimization.
Also it’s how you have codebases that could be maintained by two or three suddenly needing dozens because the testing suite needs hours to run and people even celebrate when there’s no tests in sight.
Just anecdotal personal experience. But I saw this happening inside at least 4 successful companies that started with Rails but didn’t care about those problems, and ended up wanting/having to move to something else.
I agree on the ORM abstractions causing huge performance issues, but it has nothing to do with Ruby’s dynamic method declarations.
Test suite bloat is a different problem that stems from the lack of incremental typing which I think is what ultimately killed Ruby and Rails.
Any big Rails codebase can be a nightmare to grok unless people have been diligent about documenting what different methods return.
Ridiculous comment.
But with all due respect the excitement and job market for Ruby isn't anything close to what it used to be:
[0]: https://trends.google.com/trends/explore?date=all&q=%2Fm%2F0...
Billing::Plan.find_or_create_all_by_attrs!(
standard => {1.month: 10, 1.year: 100},
pro => {1.month: 50, 1.year: 500},
enterprise => {1.month: 100, 1.year: 1000}
)Just a small Ruby syntax correction for your example:
Billing::Plan.find_or_create_all_by_attrs!(
standard: {1.month => 10, 1.year => 100},
...
)Putting this kind of type-based 'magic' in the code is a bad decision that will bite you very soon. It optimizes for being 'cute' rather than being clear and maintainable, and that's a trade-off that almost never pays off.
Here's the example that runs in hundreds of integration tests:
expect(billing_pricing_plans).to eq billing_plans(
1.month => [:free, :premium, :pro, :enterprise],
1.year => [:free, :premium, :pro, :enterprise]
)
But, in principle I agree billing, even the simple SaaS stuff, is much harder than most people expect it to be in 2025. My product (linked in the original article) is based completely on Stripe Billing - and it is still very hard to avoid all the footguns.
For people wondering, I even have an example how wrong it can go: I "audited" a successful SaaS I know uses custom Stripe billing. I paid $30 for a starter plan, but was able to "upgrade" to $2k plain for free. Here's the full video: https://www.youtube.com/watch?v=YuXp7V4nanU
bill = FactoryBot.create(:bill, products: [])
expect(bill.currency).to eq("USD")
How would you then call the objects that store costs and billing frequency? :)
Here's what Stripe uses:
- Product: "describes the goods or services". This is where you define a (plan) name and features.
- Price: defines the amount, currency, and (optional) billing interval. Since interval is optional, Prices can be used to define both recurring, and one-off purchases.
Technically, using Prices for recurring, and one-off payments is a brilliant idea. The problem is, no one refers to recurring payments as "prices". Everyone calls a "$50 per year" option a "plan".
Billing::Plan::Factory.find_or_create_by!(
name: :pro,
interval: 1.month,
amount: 50
)
Ruby itself mostly uses it for mutating methods (e.g. #gsub("a", "b") replaces the character a with b in a string and returns a new string, but #gsub!("a", "b") mutates the original.
It's not that different from `1.times` or `90.chr` which are vanilla Ruby.
> HashWithIndifferentAccess
HashWithIndifferentAccess was an unfortunate necessity to avoid DOS attacks when Symbols used to be immortal. There's no longer a reason to use it today, except for backward compatibility.
Yes, "everything is an object" is an essential insight to understanding ruby.
The exclamation mark is a convention. It is used whenever a method could possibly result in an exception being raised. Sometimes it's instead used for non-idempotent methods.
"3.days", etc are Rails things. A lot of non-Rubyists don't like it but once you use it for long enough you tend to really grow to it.
As for HashWithIndifferentAccess, yes this is generally acknowledged as a mistake in Ruby's design and is rarely used in my experience. Originally, all Ruby hashes were HWIA. When they finally realized this was a design mistake they had to create HWIA for some level of backwards compatibility
I don't know its history well enough, but it seems to originate from Lisp. PG wrote about it before [1].
It can result in code that is extremely easy to read and reason about. It can also be incredibly messy. I have seen lots of examples of both over the years.
It is the polar opposite of Go's philosophy (be explicit & favour predictability across all codebases over expressiveness).
If there is a DSL such as Rails’ URL routing, which will be the same in every app—this is also fine.
When one makes 100s of micro-DSLs for object creation, that are only ever used in one or two places—this is pure madness.
But nobody forces you to use a DSL such as rails, so I am not sure why ruby should be hated for this when it is a rails dev who does that.
The blog has much more to do with rails than ruby; such API design is really strange.
I don't think this design causes problems as such, but it is too verbose and way too ugly. To me it seems that they are just shuffling data structures around; that could even be solved via yaml files.
Of course you can try to convince them otherwise, or just be an asshole and mass-refactor to remove the DSLs.
But this kind of code is part of Ruby’s culture now.
The simple answer for anyone that doesn’t like this style is to leave Rails and Ruby for people who enjoy it.
It’s fine to hate it and want to distance yourself from it.
```rb
[:red, 1.month, 10]
[:red, 1.year, 120]
[:blue, 1.month, 120]
[:blue, 1.year, 300]
Every possible attribute (name, interval, amount) has at least two objects that share a value
If you want to make it even shorter, you have a few options - it really just comes down to preference:
# Option 1. my personal favorite, follows structure of
# intervals and plans on a pricing page.
1.month => {red: 10, blue: 120},
1.year => {red: 120, blue: 300}
# Option 2. this is fine too
red: {1.month => 10, 1.year => 120},
blue: {1.month => 120, 1.year => 300}
# Option 3. possible and works, but hurts my brain, NOT recommended
10 => {red: 1.month},
120 => {red: 1.year, blue: 1.month},
300 => {blue: 1.year}
Just a note: if you try to create two plans with the same attributes, that would error because of ActiveRecord uniqueness validations (and DB constraints). No point in having multiple identical plans.
Now every library, company or code base has its own pattern and you have to learn its pit falls. Better to learn once, cry once and just deal with it imo.
As they say, good enough is the enemy of perfection.
"Friendly Attributes" is not the "new way", not to be used "everywhere now", does not "apply to all scenarios".
If you like it, maybe you'll use it once in the next five years when the opportunity arises.
This is just using operator overloading to determine keywords, but it locks you out of ever using the same type twice in your signature. Notice that :usd turns into a name. What?
This is cute, but has no place in a professional software interface.
I don't see how you drew that conclusion. It seems to me the author provided several examples of this not being the case. Care to elucidate?
Or, as Patrick McKenzie used to tell us over and over, “charge more”.
(Yes, yes, I know some situations, customers, product, thinking, etc are different. But with broad brushstrokes, my advice is to not even entertain such a low price.)
If you are selling software, don't be the person charging $10/month. It's hard to make that business work.
Be the person charging $50/month. It's still hard - any business is - but it's much easier to make a software business financially viable if you charge decent money.
Which leads me to another piece of advice: don’t do B2C. Sell to businesses who will be far more willing to pay higher prices, will churn at a lower rate, and will - in general - require less support.