Hi all.

I want to develop a plugin system within my program, and I have a trait that functions defined by plugins should implement.

Currently, my code gets all the functions in a HashMap and then calls them by their name. Problem is, I have to create that hashmap myself by inserting every function myself.

I would really appreciate it if there was a way to say, suppose, all pub members of mod functions:: that implement this trait PluginFunction call register(hashmap) function. So as I add more functions as mod in functions it’ll be automatically added on compile.

Pseudocode:

Files:

src/
├── attrs.rs
├── functions
│   ├── attrs.rs
│   ├── export.rs
│   └── render.rs
├── functions.rs
├── lib.rs

Basically, in mod functions I want:

impl AllFunctions{
    pub fn new() -> Self {
       let mut functions_map = HashMap::new();[[
       register_all!(crate::functions::* implementing PluginFunction, &mut functions_map);
       Self { function_map }
  }
}

Right now I’m doing:

impl AllFunctions{
    pub fn new() -> Self {
       let mut functions_map = HashMap::new();[[
       crate::functions::attrs::PrintAttr{}.register(&mut functions_map);
       crate::functions::export::ExportCSV{}.register(&mut functions_map);
       crate::functions::render::RenderText{}.register(&mut functions_map);
       // More as I add more functions
       Self { function_map }
  }
}
  • Giooschi@lemmy.world
    link
    fedilink
    English
    arrow-up
    8
    ·
    3 months ago

    No, macros can see only the tokens you give them. They have no notion of the fact that crate::functions is a module, that PluginFunction is a trait and that functions_map is a variable. Not even the compiler may know those informations when the macro is expanded.

    If you really really want to do this, you can use something like inventory. Note that inventory uses a special linker section to do this, which some consider a hack. This is also not supported on WASM if you want to target it.

    • thevoidzero@lemmy.worldOP
      link
      fedilink
      arrow-up
      2
      ·
      3 months ago

      Thank you. I just put the call with !, I don’t necessarily want a macro solution. Any solution is acceptable, my requirement is that I can just keep adding more mods with functions in src/functions/ and not have to register each function.

      Inventory seems like the solution I am looking for. Although in my case, instead of collecting different values of the same type, I want to collect different types that all have same trait. But maybe I can make a temporary struct with Box<dyn _> member to collect it if trying to collect it directly doesn’t work. I do not plan to support WASM. I am planning to make C/C++ and Python API for the libraries though, so if it has problems with them, then I might have a problem.

      • taladar@sh.itjust.works
        link
        fedilink
        arrow-up
        2
        ·
        3 months ago

        Maybe keep maintaining the HashMap you have now and use one of these less portable mechanisms in a test to alert you when you forgot to register one?

        • thevoidzero@lemmy.worldOP
          link
          fedilink
          arrow-up
          1
          ·
          3 months ago

          That seems like a good compromise if I don’t find something better. Thank you.

          I’m hoping to make it easy for people to add more functions, that’s why I want minimal code change required to add more functions.