Provides a way to define an interface (trait) in a crate, but can implement or use it in any crate. It 's usually used to solve the problem of circular dependencies between crates.
// Define the interface #[crate_interface::def_interface] pub trait HelloIf { fn hello(&self, name: &str, id: usize) -> String; } // Implement the interface in any crate struct HelloIfImpl; #[crate_interface::impl_interface] impl HelloIf for HelloIfImpl { fn hello(&self, name: &str, id: usize) -> String { format!("Hello, {} {}!", name, id) } } // Call `HelloIfImpl::hello` in any crate use crate_interface::call_interface; assert_eq!( call_interface!(HelloIf::hello("world", 123)), "Hello, world 123!" ); assert_eq!( call_interface!(HelloIf::hello, "rust", 456), // another calling style "Hello, rust 456!" );The procedural macros in the above example will generate the following code:
// #[def_interface] pub trait HelloIf { fn hello(&self, name: &str, id: usize) -> String; } #[allow(non_snake_case)] pub mod __HelloIf_mod { use super::*; extern "Rust" { pub fn __HelloIf_hello(name: &str, id: usize) -> String; } } struct HelloIfImpl; // #[impl_interface] impl HelloIf for HelloIfImpl { #[inline] fn hello(&self, name: &str, id: usize) -> String { { #[inline] #[export_name = "__HelloIf_hello"] extern "Rust" fn __HelloIf_hello(name: &str, id: usize) -> String { let _impl: HelloIfImpl = HelloIfImpl; _impl.hello(name, id) } } { format!("Hello, {} {}!", name, id) } } } // call_interface! assert_eq!( unsafe { __HelloIf_mod::__HelloIf_hello("world", 123) }, "Hello, world 123!" );