Trait OptionInsertExt 

pub trait OptionInsertExt<T> {
    // Required method
    fn get_or_try_insert_with<F, E>(&mut self, f: F) -> Result<&mut T, E>
       where F: FnOnce() -> Result<T, E>;
}

Extends Option with get_or_try_insert_with.

Required Methods

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

where F: FnOnce() -> Result<T, E>,

If the option is None, 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 mutable reference to the contained value.

Examples

use try_insert_ext::OptionInsertExt;

let mut x = None;

{
    let e: Result<&mut u32, ()> = x.get_or_try_insert_with(|| Err(()));
    assert!(e.is_err());
    let y: Result<&mut u32, ()> = x.get_or_try_insert_with(|| Ok(5));
    assert_eq!(y, Ok(&mut 5));

    *y.unwrap() = 7;
}

assert_eq!(x, Some(7));

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> OptionInsertExt<T> for Option<T>

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

where F: FnOnce() -> Result<T, E>,

Implementors