1 unstable release
0.1.0 | Jan 19, 2023 |
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#1408 in Rust patterns
8KB
115 lines
another-visitor
A crate that lets you derive visitor pattern implementations for your structs.
Made because I couldn't find an existing crate supporting the exact pattern I wanted.
The general flow is inspired by how it works in ANTLR4:
- Visitor has a return type that all visit_* fns return
- Allows only implementing visit fns for some types in the tree (defaults to visiting all children)
- Allows manually visiting children if you do implement a visit fn for a type
- Allows mutation (using VisitableMut and VisitorMut)
#[derive(Visitable)]
struct A {
b1: B,
b2: B,
}
#[derive(Visitable)]
struct B {
#[visit(skip)]
msg: String
}
#[derive(Visitor)]
#[visit(A, B)]
struct AVisitor {}
impl VisitorHelper for AVisitor {
type Output = String;
}
impl AVisitor {
fn visit_a(&mut self, a: &A) -> <Self as VisitorHelper>::Output {
format!("(A {} {})", self.visit(&a.b1), self.visit(&a.b2))
}
fn visit_b(&mut self, b: &B) -> <Self as VisitorHelper>::Output {
format!("(B {})", b.msg)
}
}
fn main() {
let dat = A {
b1: B { msg: "Hello".into() },
b2: B { msg: "World!".into() },
};
let mut vis = AVisitor {};
println!("{}", vis.visit(&dat)); // => "(A (B Hello) (B World!))"
}
See another-visitor/examples for more examples.
TODO
- Derive Visitable(Mut) for more types (only basic structs and enums are supported)
- Visitable(Mut) impls for more std containers
- Good error messages in proc macros
- Documentation
- Publish to crates.io
This project is a WIP, if you have suggestions for changes or new features, please open an issue!
Licenses
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
Dependencies
~1.5MB
~36K SLoC