On-demand functions using macros

[steveklabnik]

Issue by s-panferov
Monday Oct 20, 2014 at 18:12 GMT

For earlier discussion, see rust-lang/rust#18191

This issue was labelled with: B-RFC in the Rust repository

---

I started to write some simple ORM for test purposes and i'm very interested in ability to make some dynamic code generation that could replace Ruby's method_missing.

Pseudo-code to illustrate the idea:

impl UserModel {
    pub fn macro_method (find_by, $($field_name:ident)_and_+) (&self, $($field_value:expr),+) -> SelectQuery {
        self.select_all().where_(
            $(
                self.$field_name().is($field_value),
            )   
        )
    }
}

let query = user_model.find_by_id!(100u);
let query = user_model.find_by_first_name_and_last_name!("Luke", "Skywalker");

What do you think about that? I you not interested please close this issue and never mind.

[mneumann]

I think this could be implemented right now with a find_by! marco. Usage would look like this (not sure if macros work with dot-notation):

user_model.find_by!( id = 100u );
user_model.find_by!( first_name = "Luke", last_name = "Skywalker" );

[kennytm]

This is currently a syntax error.

error: expected one of `.`, `::`, `;`, `?`, `}`, or an operator, found `!`
 --> <anon>:3:23
3 |>     user_model.find_by!( id = 100u );
  |>                       ^

[Centril]

Closing in favor of #2442.