Trait SetInsertExt 

pub trait SetInsertExt<T> {
    // Required method
    fn get_or_try_insert_with<Q, F, E>(
        &mut self,
        value: &Q,
        f: F,
    ) -> Result<&T, E>
       where T: Borrow<Q>,
             Q: Hash + Eq + ?Sized,
             F: FnOnce(&Q) -> Result<T, E>;
}

Extends sets with get_or_try_insert_with.

Required Methods

fn get_or_try_insert_with<Q, F, E>(&mut self, value: &Q, f: F) -> Result<&T, E>

where T: Borrow<Q>, Q: Hash + Eq + ?Sized, F: FnOnce(&Q) -> Result<T, E>,

If the set does not contain the value, computes the value from f. If f returns Ok, inserts the value. If f returns Err, returns the error. If there is no error, returns a reference to the contained value.

Examples

use std::collections::HashSet;

use try_insert_ext::SetInsertExt;

let mut set: HashSet<String> = ["cat", "dog", "horse"]
    .iter()
    .map(|&pet| pet.to_owned())
    .collect();

assert_eq!(set.len(), 3);
let value = set.get_or_try_insert_with("error", |_| Err(()));
assert!(value.is_err());
for &pet in &["cat", "dog", "fish"] {
    let value = set.get_or_try_insert_with::<_, _, ()>(
        pet,
        |pet| Ok(pet.to_owned()),
    );
    assert_eq!(value, Ok(&pet.to_owned()));
}

assert_eq!(set.len(), 4);

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl<T, S> SetInsertExt<T> for HashSet<T, S>

where T: Eq + Hash, S: BuildHasher,

fn get_or_try_insert_with<Q, F, E>(&mut self, value: &Q, f: F) -> Result<&T, E>

where T: Borrow<Q>, Q: Hash + Eq + ?Sized, F: FnOnce(&Q) -> Result<T, E>,

Implementors