Calling for Veteran Macro user or guru for questions/help

Hello there everyone,

I’ve been working on this pet project for a while now. It’s a very interesting idea, the concept is around a content sharing platform but instead of each person having a personalized feed that they can scroll through, the content exists in locations that can be explored by users.

Here is the repo to the project

One of the core concepts in this platform are actions that can be taken by users, right now to handle all the actions I define functions in a module I call Ruleset.Basic. This seems to work well for now however I can see this will get out of hand as I’m going to be defining more functionality, furthermore I envisioned this platform with extendible and composable rulesets, where one can define actions on separate modules (ideally using some macros to make them cleaner) and then one could put these actions into a ruleset module. By doing something like

defmodule SomeRuleset do
  use Ruleset
  register_actions [ActionModule1, ActionModule2, ActionModule3]
  # Other ruleset functionality

I tried to work on the DSL to come up with how I would ideally like to define these actions and some expriments are here and here.

I would like to ask of the community if they could help me figure this out.

The requirements are:

  1. Defining actions is clean and effortless to do
  2. Actions defined can be included in different ruleset modules
  3. Undefined functionality defaults to doing nothing

One solution I came up with while writing this would be to use structs as a basis to define the functions in the end. That would require writing less macros and seems it could be quite extendible and flexible.

Something among the lines

  name: :some_action,
  cost: 20,
  on_action_taken: fn exlorer, action -> "updates on explorer on action taken" end,
  valid_when: fn exlorer, action -> "validation before taking action" end,
  reaction: %{
    journey: [affect: :location]
  affects: %{
    exlorer: fn exlorer, action -> "updates on explorer on action passed" end,
    location: fn location, action -> "updates on explorer on action passed"

And then this struct could be used to define the functions with much less fuzz than having several macros one for each key we have here.

Would the former make sense? Would it be a good solution to problem?

Thank you for taking the time to read, Is anyone with interest in helping me figure out an ellegant solution?
Also if anyone find the project a cool idea and want to help out in any way let me know. There is lots to do still and any help is appreciated!!

I would suggest you build the functionality without macros first. Take the time to come up with some examples covering your intended usecases quite well (you know some simple ones, some complex, …). When you‘re done it‘ll be way easier to see where exactly macros can provide more succinct means of writing those modules.


@LostKobrakai Hey, The functionality without macros is already written, it’s in the Ruleset.Basic module as I pointed out. The reason I want to start generating code is because I can already see that it will be hard to maintain otherwise. Furthermore some of the things I want seem to be imposible without using AST to dynamically define some of the functions.

These would include

  1. Composable rulesets
  2. Grouped action definition without complains from compiler

I have 3 actions right now, but I can easily see 10-20 or even 100 different types of actions, or even same actions with different costs/outcomes and that would not make sense to continue coding down the path I am

But you are right that maybe I can continue to work on this and define some more actions before going about trying to use macros or other types of code definition. Even though I feel this is the time to do so, as a lot of future work will now involve actions

Sorry to be reviving this thread. I just wanted to say I managed to solve the abstraction without macros.
All I use is modules behaviors and a bit of metaprogramming. I am sure protocols would also do but I have had less experience with them. I might be writing an article about the app next week so anyone interested stay tuned :slight_smile:

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