Languages like Java/C# leave little for the compiler to prove regarding the "well-definedness" of a program, this in term leaves the programmer to dynamically verify more properties of their code, I would also like to argue that current OOP languages worsen the challenges of this task by the programmer. OOP doesn't necessarily have to be bad, I think that these issues can be fixed by a more restricitve type system.
I understand that this a very controversial opinion but hear me out, maybe I am wrong regarding this. But these are my personal frustrations with OOP and my personal experiences with OOP. Perhaps I am entirely wrong on this, perhaps I am blaming OOP where I should really be blaming Programmers.
Important thing to note here: When I am talking about OOP I'm really talking about the popular implementations of OOP like Java/C# and not Smalltalk.
Another note: I may be wrong about C#, I have made an assumption here that it is essentially Java with nicer syntax, based upon the comments I have heard from developers.
Your program at a very abstract level, is something that takes in data and outputs data. By dataflow I am talking about the steps data takes from the moment it enters a program to the moment it leaves the program. It is essentially how data flows through the control flow graph (CFG) of your program.
This is important to note, because my reasons for disliking OOP largely revolve around dataflow.
Object Oriented Programming revolves around how to structure entities. functions that change these entities are bundled together with the entity but they really are second class citizens.
But the important thing to note here is that how you structure entities isn't really the hardest problem in programming, in fact in my experience it has almost always been the easiest thing to do, but it may well be that I have not worked in a complex enough codebase yet.
In my opinion the hardest problem in software engineering is managing your control flow graph from getting too complex. This is important because it is the biggest thing that impacts readability. If your data jumps too much around your CFG, then your code likely is hard to understand. The tools that OOP provide, help with abstraction at the cost of your CFG complexity. With OOP you usually have references to the objects you want to mutate, this basically means your CFG looks incredibly complex, it is essentialy a denser graph than what it could have been with FP for example.
OOP as it is presented in languages today such as Java and C# encourage too much mutable state, mutable state can get increasingly hard to manage. I think this is especially true when concurrent mutation of state is introduced, it becomes incredibly hard to juggle all the possible state mutations in your head. Haskell for example with STM really shines here, Rust as well, excels here, both present excellent solutions to concurrent state modification. Once again this can be blamed on the programmer, but a good paradigm should stop yourself from shooting yourself in the foot.
OOP's promise of hiding implementation details is not a good one in a system where mutable state is present. We can't really be completely sure about what the code will do, any developer is free to change code and may not satisfy our assumptions about that implementation we still have to go and read the code just to be sure of what the code is doing. This may not always be true, if you have a type system that enforces contracts (Design by Contract, also see the Eiffel programming language) I think OOP would fare better here, but it still doesn't prevent every possible scenario.
I'm going to go against what a lot of people usually say, for me personally it is easier and cleaner to repeat myself than to deal with abstractions.
This may be surprising given that I have wrote quite a bit on how OOP is awful
and you should never use it. I don't think OOP necessarily forces bad code, I
simply think that the current popular implementations of OOP are bad. In my
opinion something like Smalltalk is still better in some ways than Java/C#,
fact the inventor of OOP, Alan Kay stated that the big idea with OOP is message passing,(Hillel Wayne refutes that Kay made this claim) something both languages don't really focus on.
Besides this, I don't believe that there can't exist an OOP language that avoids some of the issues that I have talked about above. I personally think a more expressive type system is the key to a good modern OOP language.
Rust is one language that solved the problem C/C++ has through an advanced type system, I genuinely think that an advanced type system could also solve the issues that I have outlined above.
I really like this. What Adam argues for makes sense, I do really love some of his points. I think for me the most important features are:
What is better than OOP?
Procedural Programming has its own problems but OOP isn't immune from these issues either, this is why in my opinion Procedural Programming can be better than OOP, simply because it reduces the amount of issues a language has.
Functional Programming can be better than both Procedural Programming and OOP in my opinion simply because it controls very explicitly the complexity of your control flow graph. Your data flows through the CFG in a very linear fashion, this. It isn't perfect, it can be awkward or even impossible to model some imperative datastructures here, and even when there are escape hatches, they are awkward to use.
I hope everyone was able to agree or disagree without too much frustration or anger and that this is somewhat easy to understand but I don't entirely think I've organised my thoughts very well. This is something I deeply think about and I'd be happy to continue the discussion somewhere else.
Please check the resources section below, I think these authors have outlined these issues better than I have.