Easy self-referential struct generation for Rust. Dual licensed under MIT / Apache 2.0.
Note: Version 0.7.0 removed the with_*_contents and borrow_*_contents functions, replacing
them with with_* and borrows_* functions that work similar to functions with those names in
earlier versions. In other words, there is no longer seperate semantics for accessing tail fields
and immutably borrowed fields. See the documentation for a full explanation.
Note: as of September 2020, there is a limitation in Rust's type checker which prevents structs with chained references from compiling properly. (E.G. you cannot have a struct where field C refers to field B which refers to field A.) Refer to the documentation on chain_hack for a workaround for this problem.
Tests are located in the examples/ folder because they need to be in a crate outside of ouroboros
for the self_referencing macro to work properly.
use ouroboros::self_referencing;
#[self_referencing]
struct MyStruct {
int_data: Box<i32>,
float_data: Box<f32>,
#[borrows(int_data)]
int_reference: &'this i32,
#[borrows(mut float_data)]
float_reference: &'this mut f32,
}
fn main() {
let mut my_value = MyStructBuilder {
int_data: Box::new(42),
float_data: Box::new(3.14),
int_reference_builder: |int_data: &i32| int_data,
float_reference_builder: |float_data: &mut f32| float_data,
}.build();
// Prints 42
println!("{:?}", my_value.borrow_int_data());
// Prints 3.14
println!("{:?}", my_value.borrow_float_reference());
// Sets the value of float_data to 84.0
my_value.with_mut(|fields| {
**fields.float_reference = (**fields.int_reference as f32) * 2.0;
});
// We can hold on to this reference...
let int_ref = *my_value.borrow_int_reference();
println!("{:?}", *int_ref);
// As long as the struct is still alive.
drop(my_value);
// This will cause an error!
// println!("{:?}", *int_ref);
}