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Those are fair points. In terms of PRing, though, I do think that people are a little too "afraid" of macros. It sometimes feels like people won't learn them

Those are fair points. In terms of PRing, though, I do think that people are a little too "afraid" of macros. It sometimes feels like people won't learn them out of of principle which is a shame as they aren't that complicated. Though anyone trying to navigate nested macros definitely has my sympathy. No matter how slice it, however, macros are a massive part of what makes Elixir Elixir. A large portion of the language's "keywords" are just macros and they reduce a lot of the boilerplate Erlang forces you to write.

throwawaymaths 3y ago
EEx does macros well. Note that EEx.function_from_x makes you declare the name of the function it instantiates, so it's searchable. GenServer is kind of a "bad example" of a macro. It creates a totally hidden function. Though I guess to be fair 99.9% of the time you really shouldn't be writing genservers in elixir.
- AlchemistCamp 3y ago
  > 99.9% of the time you really shouldn't be writing genservers in elixir Woah! Why is that? I've written at least one GenServer in nearly all the Elixir projects I've worked on. They seem like one of the base building-blocks to me. Also, if you squint a bit, you'll see that many libraries you're working with are essentially exposing a GenServer interface, with a few extra features.
  - sodapopcan 3y ago
    > Also, if you squint a bit, you'll see that many libraries you're working with are essentially exposing a GenServer interface, with a few extra features. Like LiveViews :)
  - pests 3y ago
    The only thing I can think of is when developers overuse genserver not realizing it's involving another process and then serializing your requests (behind a queue even) into its mailbox. That may be desirable for some but in-process handling can sometimes be the better choice.
  - throwawaymaths 3y ago
    I've never written a genserver in any professional project I've worked on.... Well, except maybe for a trivial 5 line wrapper enables a global ets. > Also, if you squint a bit, you'll see that many libraries you're working with are essentially exposing a GenServer interface, with a few extra features. I never said you shouldn't be using GenServers. I said you shouldn't write GenServers.
    - sodapopcan 3y ago
      There's no reason not to write GenServers if you need them. Just don't use them as a class replacement :) But if you need to model some simple runtime state or concurrency, that's what they're there for.
      - throwawaymaths 3y ago
        use Tasks for simple concurrency, Jose has built an awesome module for us.
        sodapopcan 3y ago
        Oh I agree! I have a couple of gen servers acting as very simple message queues—the kind that don't matter if they are nuked during a deploy.
    - deleted 3y ago
      [deleted]
    - jolux 3y ago
      > I've never written a genserver in any professional project I've worked on Wow, that's quite surprising! We use GenServers quite extensively at work. The most interesting usage is probably this application, which uses GenServers to model the state of real-world hardware (in this case, transit stop countdown clocks): https://github.com/mbta/realtime_signs/blob/main/lib/signs/supervisor.ex https://github.com/mbta/realtime_signs/blob/main/lib/signs/s... Curious what you use instead of GenServers. Plain processes? Agents? Something else? GenServers are probably overused but I still reach for them when I need a concurrent bundle of state with a specific interface and behavior. I think we're generally trying to write more GenStages than GenServers at the MBTA these days, but that's mainly because we're moving towards being event-driven. GenServers still have their place.
- dqv 3y ago
  >It creates a totally hidden function. Are you talking about child_spec/1? `use GenServer` honestly provides some pretty good QoL enhancements over `@behaviour GenServer`. I don't know when or if there was a change to recommending `use GenServer`, but I was pleasantly surprised when I started using it. Especially because I'm not writing new GenServers all the time, having guard rails is nice to avoid being slowed down by remembering all the boilerplate: init/1, handle_x/y, child_spec/1 It's even nice enough to give additional information about why its crashing so you don't get confused why e.g. the handle_call function is working. I make this mistake almost every time I write a new GenServer: def handle_call(:ping, state) do {:reply, :pong, state} end Before, you would just get this meaningless gen_server stacktrace that basically just says "it crashed lol". Now you get the additional hint of "hey you didn't define handle_call/3" when it crashes.
  - throwawaymaths 3y ago
    Last I checked you need to do init/1 by hand. Honestly being more transparent about creating child_spec like `GenServer.create_default_child_spec` would be great. The rest of use GenServer is pretty good, IMO (this is why I wrote 'kind of a bad' macro). I normally hate default implementation of functions but defaulting with an error saying "you forgot this" is reasonable. Edit: just checked, it warns if you don't... I have compiler warnings as error on all my personal projects so that's why I thought you had to do it manually

throwawaymaths 3y ago

EEx does macros well. Note that EEx.function_from_x makes you declare the name of the function it instantiates, so it's searchable. GenServer is kind of a "bad example" of a macro. It creates a totally hidden function. Though I guess to be fair 99.9% of the time you really shouldn't be writing genservers in elixir.

AlchemistCamp 3y ago
> 99.9% of the time you really shouldn't be writing genservers in elixir Woah! Why is that? I've written at least one GenServer in nearly all the Elixir projects I've worked on. They seem like one of the base building-blocks to me. Also, if you squint a bit, you'll see that many libraries you're working with are essentially exposing a GenServer interface, with a few extra features.
- sodapopcan 3y ago
  > Also, if you squint a bit, you'll see that many libraries you're working with are essentially exposing a GenServer interface, with a few extra features. Like LiveViews :)
- pests 3y ago
  The only thing I can think of is when developers overuse genserver not realizing it's involving another process and then serializing your requests (behind a queue even) into its mailbox. That may be desirable for some but in-process handling can sometimes be the better choice.
- throwawaymaths 3y ago
  I've never written a genserver in any professional project I've worked on.... Well, except maybe for a trivial 5 line wrapper enables a global ets. > Also, if you squint a bit, you'll see that many libraries you're working with are essentially exposing a GenServer interface, with a few extra features. I never said you shouldn't be using GenServers. I said you shouldn't write GenServers.
  - sodapopcan 3y ago
    There's no reason not to write GenServers if you need them. Just don't use them as a class replacement :) But if you need to model some simple runtime state or concurrency, that's what they're there for.
    - throwawaymaths 3y ago
      use Tasks for simple concurrency, Jose has built an awesome module for us.
      - sodapopcan 3y ago
        Oh I agree! I have a couple of gen servers acting as very simple message queues—the kind that don't matter if they are nuked during a deploy.
  - deleted 3y ago
    [deleted]
  - jolux 3y ago
    > I've never written a genserver in any professional project I've worked on Wow, that's quite surprising! We use GenServers quite extensively at work. The most interesting usage is probably this application, which uses GenServers to model the state of real-world hardware (in this case, transit stop countdown clocks): https://github.com/mbta/realtime_signs/blob/main/lib/signs/supervisor.ex https://github.com/mbta/realtime_signs/blob/main/lib/signs/s... Curious what you use instead of GenServers. Plain processes? Agents? Something else? GenServers are probably overused but I still reach for them when I need a concurrent bundle of state with a specific interface and behavior. I think we're generally trying to write more GenStages than GenServers at the MBTA these days, but that's mainly because we're moving towards being event-driven. GenServers still have their place.
dqv 3y ago
>It creates a totally hidden function. Are you talking about child_spec/1? `use GenServer` honestly provides some pretty good QoL enhancements over `@behaviour GenServer`. I don't know when or if there was a change to recommending `use GenServer`, but I was pleasantly surprised when I started using it. Especially because I'm not writing new GenServers all the time, having guard rails is nice to avoid being slowed down by remembering all the boilerplate: init/1, handle_x/y, child_spec/1 It's even nice enough to give additional information about why its crashing so you don't get confused why e.g. the handle_call function is working. I make this mistake almost every time I write a new GenServer: def handle_call(:ping, state) do {:reply, :pong, state} end Before, you would just get this meaningless gen_server stacktrace that basically just says "it crashed lol". Now you get the additional hint of "hey you didn't define handle_call/3" when it crashes.
- throwawaymaths 3y ago
  Last I checked you need to do init/1 by hand. Honestly being more transparent about creating child_spec like `GenServer.create_default_child_spec` would be great. The rest of use GenServer is pretty good, IMO (this is why I wrote 'kind of a bad' macro). I normally hate default implementation of functions but defaulting with an error saying "you forgot this" is reasonable. Edit: just checked, it warns if you don't... I have compiler warnings as error on all my personal projects so that's why I thought you had to do it manually