# On-demand functions using macros
**URL:** https://internals.rust-lang.org/t/on-demand-functions-using-macros/681
**Category:** ideas (deprecated)
**Created:** [October 21, 2014, 5:17am UTC](https://internals.rust-lang.org/t/on-demand-functions-using-macros/681 "2014-10-21T05:17:43Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@s\_panferov](https://internals.rust-lang.org/u/s_panferov)
#### Post date: [October 21, 2014, 5:17am UTC](https://internals.rust-lang.org/t/on-demand-functions-using-macros/681/1 "2014-10-21T05:17:44Z")
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:
```rust
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.
---
### Author:  [@stebalien](https://internals.rust-lang.org/u/stebalien)
#### Post date: [October 21, 2014, 6:25am UTC](https://internals.rust-lang.org/t/on-demand-functions-using-macros/681/2 "2014-10-21T06:25:37Z")
Why not:
1. Builder style (methods generated with by a compiler plugin): `UserModel.where().first_name("Luke").and().last_name("Skywalker")`
2. Macro style: `query!(UserModel where first_name is "Luke" and last_name is "Skywalker")` (basically typesafe SQL).
---
### Author:  [@system](https://internals.rust-lang.org/u/system)
#### Post date: [March 25, 2019, 8:23am UTC](https://internals.rust-lang.org/t/on-demand-functions-using-macros/681/3 "2019-03-25T08:23:01Z")
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