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Write More Classes

by someone13 on 2/12/13, 2:59 AM with 145 comments

• by haberman on 2/12/13, 6:06 AM

  I think the real point the author is trying to make is: use modular, layered designs of composable components, instead of monolithic APIs that only have a single entry point. The single-entry-point model imposes costs and decisions onto the application that are hard to work around.

  I think this is a good point. I think that it's hard to get from there to "more classes are always better" though. More classes don't always make a design more flexible. You have to consciously design for flexibility and reusability, and even then it takes a lot of deep thought and hard work to get your interfaces right, such that they are truly reusable in practice.

• by contingencies on 2/12/13, 6:06 AM

  Write no classes!

  Joe Armstrong: "I think the lack of reusability comes in object-oriented languages, not in functional languages. Because the problem with object-oriented languages is they've got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle. If you have referentially transparent code, if you have pure functions-all the data comes in its input arguments and everything goes out and leaves no state behind-it's incredibly reusable. You can just reuse it here, there, and everywhere. When you want to use it in a different project, you just cut and paste this code into your new project. Programmers have been conned into using all these different programming languages and they've been conned into not using easy ways to connect programs together. The Unix pipe mechanism-A pipe B pipe C-is trivially easy to connect things together. Is that how programmers connect things together? No. They use APIs and they link them into the same memory space, which is appallingly difficult and isn't cross-language. If the language is in the same family it's OK-if they're imperative languages, that's fine. But suppose one is Prolog and the other is C. They have a completely different view of the world, how you handle memory. So you can't just link them together like that. You can't reuse things. There must be big commercial interests for whom it is very desirable that stuff won't work together."

  - Peter Seibel, Coders at Work: Reflections on the Craft of Programming

• by 10098 on 2/12/13, 7:29 AM

  No. Don't write classes. Write useful abstractions. It doesn't matter what the abstraction is (a class, a function, or something else you programming language supports)as long as it fits your current architecture and can be easily modified for possible future extensions.(I will agree with the author that one giant monolithic function is probably a bad abstraction).

• by Locke1689 on 2/12/13, 7:05 AM

  This is a bad article.

  First, write nothing. If you can solve your problem without writing code (or even better, by deleting code), that is the best solution.

  Next, write code which fits your architecture. Sometimes functional composition is the best system for representing your computational structure. Tree operations, for example, are especially amenable to recursive function-based computation.

  Sometimes, when you are writing a state machine, for example, an object is the best possible representation. Objects are entirely focused around hidden-implementation finite state machines, and thus mirror your computation almost exactly.

  Funny how most people who have only practical training in a handful of languages and no programming language theory at all tend to advocate for the one style of programming that they know well. When all you have is a hammer...

  Note: The small paragraph at the end of this article seems to hedge by agreeing with me and essentially calling the reader to disregard what he previously wrote. If he had followed my step one he could have avoided writing the entire article. Think of the complexity saved!

• by Uchikoma on 2/12/13, 6:34 AM

  As Java was mentioned. The Java API is very nice, but there is a layer missing on top. The Java API was written with a early 90s mindset and got most users after 2000. This goes for most Java APIs. IO, Swing, ... The idea is to have LEGO building blocks (BufferedReader) you can plug together. But you need to plug them together all the time. The missing layer e.g. is IO.readIntoString(file). Apache IOUtils, StringUtils etc. fill in this layer for many Java APIs.

  The one API that is not powerful enough is Collection. There you have the top layer without the LEGO building blocks. Compare this to the Scala collection API which has the top layers and the building blocks.

  For a good API you need both, building blocks to tailer to your specific need (20% of the time) and an easy top layer (80%) to prevent writing the same stuff all the time.

• by viraptor on 2/12/13, 8:58 AM

  I really don't like the way this was presented, even if I may agree with the idea underneath. It's not about classes at all. It's about better design, but even the examples are strange.

  Just from the JSON example:

  - Why do I need a class for streaming JSON - Python's got a perfectly good `yield` for returning tokens in such situations.

  - Why would I ever design the JSON library to be extendable at the tokenizer level? If you need serialiser / deserialiser, why not just provide a map of types to callbacks / callback as a parameter? Do you really want to extend JSON format itself?

  - The 2GB JSON example is just weird. If you care about such use cases, you a) most likely have a limit on data size at webserver level, b) use proper formats for handling that size of data (I really doubt there's no better data representation once you get to GB sizes).

  I see his point of view, but he's arguing for one single "hammer" solution, rather than arguing against the monolithic design. His story seems to present some weird back-story really: "I needed to make my data easier to handle, so I started automatically serialising objects into JSON, then they became huge so I have to start streaming them otherwise just parsing of them takes way too long".

• by fab13n on 2/12/13, 8:20 AM

  There's a fairly effective rule of thumb: classes--or more accurately objects--are a way to cleanly encapsulate state. If you rely on a mutating state, you probably want an object/class. If not, a function is often better.

  Now you can bundle related functions together in a structure, but this structure is morally a module, not an object, let alone a class. Some languages will force you to encode those modules as classes / prototypes / singletons, but that's just a design pattern to circumvent a limitation of the language.

• by chewxy on 2/12/13, 4:03 AM

  You can do the same with python's msgpack as the C# version

  Try this:

      packer = msgpack.Packer()
      serialized = packer.pack('stuff you wanna pack')
        
      unpacker = msgpack.Unpacker()
      unpacker.feed(serialized)
      print unpacker.unpack()
  
  

  I had originally used this, but then as my API scope extended to more than just using msgpack, having a common API interface for json (i.e. the .loads() and .dumps() method) was found to be more useful.

  And while I agree with most of the article, I don't think writing more classes is a one-size-fits-all solution. Classes IMO, only makes sense from a heavily OOP point of view.

• by notallama on 2/12/13, 5:15 AM

  if classes didn't have such a terribly verbose syntax in basically every language that has them, i'd be less opposed to using them.

  in java, c++, or c#, to add a variable to a class, you have to repeat its name 4 times. once to declare, once in the constructor parameters, and once on each side of the assignment. why am i writing the same thing 4 times for what should be a core part of the language?

  in haskell, you write it once (i'm not saying haskell's records are nice, but they got that part right). same with rust.

  and with a function, you write it once.

• by wyuenho on 2/12/13, 10:28 AM

  People don't talk about this anymore for some reason, but I think both Jack and Armin are really just approaching API design in 2 different ways - top-down and bottom-up. The problem is, most people stick with the same approach through out and end up ignoring that programmers are mere mortals too, and they have human needs.

  Expanding on Armin's dichotomy, top-down designs like Python's open() or jquery plugins start with giving 70-80% of users APIs that are as simple as possible for their most frequent use cases while shielding them from the sausages underneath.

  Bottom-up designs like Java's standard library or POSIX start with LEGO building blocks that solve the most fundamental pieces of largely academic computer science problems and just give them out to their end users and expect them to be able to assemble Tower Defense by solving this LEGO puzzle first.

  The problem with sticking entirely to their 2 approaches is that you end up either ignoring power users or making healthy adults with normal IQs feel stupid. There is no reason you can't serve 100% of your user base by incrementally evolving your API approaches and provide 2 sets of APIs within the same library, with the top-down easy one shielding the bottom-up sausage factory that takes care of the meat grinding for you. Most API designers don't realize this and won't ever go there. Extremists and egoists with lots of opinions will spending hundreds of man years to promote their One True Way of doing things. They'll say things like "no leaky abstractions!" or "these enterprise people are just making things too complicated to create jobs!", when the simple truth is probably just that they don't understand how people think.

  Make your libraries easy to do things that are easy, but make hard things possible too.

• by splicer on 2/12/13, 4:54 AM

  Personally, I find it more natural to use closures when parsing in Python, not classes. BTW, my day job frequently involves writing parser in C.

• by comex on 2/12/13, 5:53 AM

  IMO, the Flask example is pushing it - considering how large a job rendering a template is, the number of customization points is probably appropriate, but at some point you're going to get lost in a rabbit hole of wrapper functions that call wrapper functions and end up with three equally appropriate levels you might hook into because the code was written to keep you from having to duplicate a single line of code from the library in your alternative implementation-- never mind how confusing that makes things to the casual debugger (who wants to get to the actual meaty code to see what's wrong with it). Flexibility is useful, but it must justify the loss of simplicity.

  But yes, in the JSON cases, having more flexibility than a single 'loads' is clearly justified.

• by cgopalan on 2/12/13, 6:32 AM

  By default, I go with the inclination to put code in functions when I tackle a project, because most of my projects are just products and applications without a public API and testing or debugging the flow in a functional paradigm is much simpler. I can take a function and plug it in the interactive interpreter (in Python) and run it without needing to instantiate other state that's needed for the test.

  However, in certain cases, like where I need to write a public API, I have found that having classes as wrappers to the functionality helps it a bit. So really, the "stop-writing-classes-unless-you- absolutely-need-to" guideline still holds true for me.

• by ankitml on 2/12/13, 8:55 AM

  The discussion on the thread has rotten to much extent, the article doesnt address different languages or paradigms, he just mentions about classes being better than block codes in python. Something more rudimentary, a valuable piece for quick-fix programmers, for hobby programmers. Classes are one way of abstractions.

  So he asks for using abstractions instead on no abstraction (block code) but if you have other ways of abstracting code, please go ahead. THis article is good for people with few / no tools, people who are still learning

• by redangstrom on 2/12/13, 5:49 AM

  Seems like he's asking for modularization so we can make special-case adjustments to libraries without completely monkey patching or rewriting them. Seems like a reasonable ask of a mature library.

  On the streaming verus resident working set argument... Most of what most programmers deal with doesn't have to scale to deal with huge streaming datasets, so it doesn't get the attention.

• by jakejake on 2/12/13, 6:54 AM

  I must be way out of touch because I had no idea there was an anti-class movement for which the OP has to argue for more classes?

• by pyeek on 2/12/13, 10:48 AM

  I think there is an aspect to this article that won't be understood unless you're really part of the Python community. For a while now, one of Python's selling points to users from other languages has been "you don't need to write all that code" (most likely directed at Java), more specifically you can simply use a function rather than having to define a class just to define static methods etc. Over time, this has grown into the mantra of "You don't need a class just use a function/module". A lot of people seem to follow this viewpoint blindly, so much so that they consider it to be "Pythonic"; the way you "should" write python.

  I think Armin's post is somewhat in line with the following post from the google testing blog. http://googletesting.blogspot.com/2008/12/static-methods-are...

• by Offler on 2/12/13, 9:23 AM

  Could not agree more with the idea that people should write more well designed, OO code. This exact same issue is prevalent in JS land and it leads to people saying JS can't be used for real development, when in fact the problem is that the code they write is a mess and that's what's holding them back.

• by cwp on 2/12/13, 10:53 PM

  Is there anything to this debate that doesn't boil down to style? Python has a pretty decent object system. It also has first-class, nested functions with closures. You could write good OO code or good functional code according to your taste, and python libraries don't seem to strongly prefer one style over the other. I'm not terribly interested debating OO vs. functional in the general case, but I am interested in the pros and cons of each style in specific contexts.

  For example, Python's lack of variable declarations sometimes leads to bugs involving scoping. (I've run into this a couple of times myself). Does this quirk become more of an issue in heavily functional code? Are there other language quirks that become troublesome in heavily OO code? In what circumstances might one style be preferred over another?

• by jerf on 2/12/13, 1:55 PM

  In Python, the distinction is less strong than it is in some other languages. Since a class can implement __call__, allowing instances to be directly called like a function, even if an API specifies a function, you can pass a class instance in with a suitable __call__. So using functions doesn't have to tie to to it being a function forever and ever in the future (or breaking reverse compatibility, the way it does in most other languages. This isn't a perfect answer to the objections, but the objection is at its most weak in Python.

• by INTPenis on 2/12/13, 8:45 AM

  A good example of classes in Python is the dnspython library.

  It's tasked with returning records from parsed zones and every single record is a class. I like it and I don't understand the first sentence of this blog post.

  Try not to put too much weight on what others tell you, make up your own mind. It's a classic human issue.

• by benatkin on 2/12/13, 5:57 AM

  I find that I like it when classes store configuration that's known at load time, rather than state. That way it's a lot like a Common Lisp program, except multiple programs can run in the same process, have different configurations, and communicate with each other.

• by mafro on 2/12/13, 5:50 AM

  Can anyone explain the statement about simplejson for me please?

    Some libraries manage to skip the token part. (I'm looking at you 
    simplejson, a library that even with the best intentions in mind 
    is impossible to teach stream processing)

• by Ingaz on 2/12/13, 6:20 AM

  I could not understand how classes can help with JSON-example.

  It looks the same as XML SAX vs DOM: you feed NN-Mb to DOM-parser (SQLServer xml-datatype for example) and you have problems. No matter: classes or functions.

• by quasque on 2/12/13, 4:16 PM

  I must have missed something in my reading of the article - what is the relevance of "Condoms for Onions" to the essay?

• by ehutch79 on 2/12/13, 1:04 PM

  I think the original video this is a response to, was really just saying 'A class should not be one method, that's a function'

• by iso-8859-1 on 2/12/13, 12:44 PM

  The Java would have been prettier if he had used the new try-with-resources from Java 7.

• by dakimov on 2/12/13, 7:34 AM

  The programming industry walks around in circles and there is no beacon in this darkness of ignorance.

  There is no professional culture and new generations of developers successfully forget all the experience previous generations have accumulated.

  Also, some piece of advice from a seasoned programmer to the web-programming-children: if you are not really a serious developer, if you write your freaking websitee on Django, or whatever a framework there is, you don't really need a methodology, because you are doing an easy task, you can write in whatever language/style/paradigm you like, even on Brainfuck. But please don't extrapolate your humble experience to the entire industry and don't tell people working on large complicated (real) projects how they must write code, because they have some experience you don't have.

• by leppie on 2/12/13, 7:12 AM

  So in Java, a parameter named 'filename' is automatically aliased to 'path'? Doh...

  static String readFirstLine(String filename) { try { BufferedReader br = new BufferedReader(new FileReader(path)); ....

  So people writes this everyday, yet still fail to do it correctly...

  Also, this article was written 1 day in the future. The future looks bleak to me...

• by akaru on 2/12/13, 5:26 AM

  Jesus, learn how to write before, you know, writing so much.