Comment by overgard

> Why would you not focus on writing OO code in an OO language for example?

Often people do this to deliver higher quality software. Most languages still have some OO features, and people don't use them because they know they lead to bad code. Inheritence (a core OO feature) comes to mind. Most professionals nowadays agree that it should not be used.

OO designs are often over-abstracted which makes them hard to understand and hard to change. They lack "locality of behavior". Trivial algorithms look complicated because parts of them are strewn across several classes. This is why more modern langues tend to move away from OOP.

My guess is that im the long term, what we will keep from OO is the possibility to associate methods with structs.

> Why would you not focus on writing OO code in an OO language for example?

That's circular logic. I wouldn't focus on writing OO code because I know from experience that the result is usually worse. If I had to use a language that was oriented towards writing OO code, I'd still try to limit the damage.

> There are programming paradigms for a reason

Nah. A lot of them are just accidents of history.

> Why would you not focus on writing OO code in an OO language for example? Would you start writing OO code in a functional language? No you wouldn't, because it would be pointless. There are programming paradigms for a reason

I'm paid for efficiently solving business problems with software, not using a particular paradigm. If an FP solution is more appropriate and the team can support it, then that's what I'll use.

> Why would you not focus on writing OO code in an OO language

It should be the best solution to the problem direct whether or not use of OO is best, not the language.

> Domain models are fundamentally an object-oriented programming concept.

They are not.

> You model the business domain with classes, meaning you specify in them the behavior that reflects your business domain.

I have better tools for doing that.

> In Domain-Driven design, with its basis on OO, you implement these operations at the class level, because your classes model the business domain and implement business rules.

You're still not explaining the "why". You're just repeating a bunch of dogma.

> a domain model without behavior means you are wasting all development effort building up a structure that does nothing and adds none of the benefits, and thus represents wasted effort.

I know from experience that this is completely false.

> You don't know what you're doing, and somehow you're calling it Domain-Driven design.

I don't call it domain-driven. You can call it domain-driven if you want, or not if you don't want. I don't care what it's called, I care whether it results in effective, maintainable software with low defect rates.

> Your Order class has a collection of Product items, but you can update an order, cancel a order, repeat an order, etc. This behavior should be member functions.

This is how to fuck up OO and give it a bad name:

  order.update(..) // Now your Order knows about the database.

  order.cancel(..) // Now your Order can Email the Customer about a cancellation.

  order.repeat(..) // Now your Order knows about the Scheduler.

What else could Order know about? Maybe give it a JSON renderer .toJson(), a pricing mechanism .getCost(), discounting rules .applyDiscount(), and access to customer bank accounts for .directDebit(); Logging and backup too. And if a class has 10+ behaviours you've probably forgotten 5 more.

An Order is a piece of paper that arrived in your mailbox. You can't take a sharpie to it, you can't tell it to march itself into the filing cabinet. It's a piece of paper which you.read() so that you.pack() something into a box and take it to the post office. You have behaviours and the post office has behaviours. The Order and the Box do not. At best they have a few getters() or some mostly-static methods for returning aggregate data - but even then I'd probably steer clear. For instance: if the Order gave me a nice totalPrice() method, it simplifies things for later right? Well no, because in TaxCalculator (not order.calculateTax()) I will want to drill down into the details, not the aggregate. Likewise for DiscountApplier.

> Does it make sense to have objects without behavior? No, not in OO and elsewhere as well.

It does, just like in the Domain (real-world Orders). Incidentally, I believe objects-without-behaviours is one of the core Clojure tenets.

Since this is HN's monthly UB-bashing thread, I should point out that I learnt most of this stuff from him. (It's more from SOLID though, I don't think I have much to say on about cleanliness.)

The above examples violate SRP and DI.

"Single reason to change": If order.cancel(..) knows about email, then this is code I have to change if the cancellation rules change or if the email system changes. What if we don't notify over email anymore? Order has to become aware of SMS or some other tech which will cause more reasons for change.

"Dependency inversion": People know what Orders are, regardless of technical competence. They can exist without computers or any particular implementation. They are therefore (relative to other concerns here) high-level and abstract. Orders are processed using a database, Kafka and/or a bunch of other technologies (or implementation details). DI states that abstract things should not depend on concrete things.

> Domain models are fundamentally an object-oriented programming concept

They are absolutely not. In fact, they are not even specific to even just programming, let alone OOP.

I really don't understand this fixation on domain modelling. It looks like a lot of UML mixed with a "*DD" (life-pro tip: pretty much any X Driven Development is something experienced programmers rarely care about. You can borrow good ideas from almost any methodology without becoming obsessed with its primary subject. Being obsessed with the One True Way is a great way to waste a lot of brain cells). Also nobody sane touches UML. Or makes big official charts of classes and their relationships. It's a massive waste of time. You might come up with some core concepts and relationships, like a B-REP, but you don't need some jargon-heavy official way to do this.

> The argument being made against anemic domain models is that a domain model without behavior fails to meet the most basic requirements of a domain model. Your domain model is just DTOs that you pass around as if the were value types, and have no behavior at all. Does it make sense to have objects without behavior? No, not in OO and elsewhere as well. Why? Because a domain model without behavior means you are wasting all development effort building up a structure that does nothing and adds none of the benefits, and thus represents wasted effort. You are better off just doing something entirely different which is certainly not Domain-Driven design.

I have barely any idea what you're saying, but I will agree that I'm probably better off without DDD.

> You are adopting a OO concept, which the most basic traits is that it models business domains with objects. Do you understand the absurdity of this sort of argument?

Except I'm not, because I don't care about DDD? My argument is simply: caring how much your code adheres to some third party methodology doesn't matter, what matters is if you're writing good code or not.