Trait OptionExt

pub trait OptionExt<T> {
    // Required methods
    fn owned(&self) -> Option<<<T as Deref>::Target as ToOwned>::Owned>
       where T: Deref,
             T::Target: ToOwned;
    fn display_or<D>(self, default: D) -> Either<T, D>
       where T: Display,
             D: Display;
    fn display_or_else<D, R>(self, default: D) -> Either<T, R>
       where T: Display,
             D: FnOnce() -> R,
             R: Display;
}

Extension methods for std::option::Option.

Required Methods

fn owned(&self) -> Option<<<T as Deref>::Target as ToOwned>::Owned>

where T: Deref, T::Target: ToOwned,

Converts from Option<&T> to Option<T::Owned> when T implements ToOwned.

The canonical use case is converting from an Option<&str> to an Option<String>.

The name is symmetric with Option::cloned.

fn display_or<D>(self, default: D) -> Either<T, D>

where T: Display, D: Display,

Returns a type that displays the option’s value if it is present, or the provided default otherwise.

Examples

use mz_ore::option::OptionExt;

fn render(number: Option<i32>) -> String {
    format!("Your lucky number is {}.", number.display_or("unknown"))
}

assert_eq!(render(Some(42)), "Your lucky number is 42.");
assert_eq!(render(None), "Your lucky number is unknown.");

fn display_or_else<D, R>(self, default: D) -> Either<T, R>

where T: Display, D: FnOnce() -> R, R: Display,

Like OptionExt::display_or, but the default value is computed only if the option is None.

Examples

use mz_ore::option::OptionExt;

fn render(number: Option<i32>, guess: i32) -> String {
    format!(
        "Your lucky number is {}.",
        number.display_or_else(|| format!("unknown (best guess: {})", guess)),
    )
}

assert_eq!(render(Some(42), 7), "Your lucky number is 42.");
assert_eq!(render(None, 7), "Your lucky number is unknown (best guess: 7).");

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<T> OptionExt<T> for Option<T>

fn owned(&self) -> Option<<<T as Deref>::Target as ToOwned>::Owned>

where T: Deref, T::Target: ToOwned,

fn display_or<D>(self, default: D) -> Either<T, D>

where T: Display, D: Display,

fn display_or_else<D, R>(self, default: D) -> Either<T, R>

where T: Display, D: FnOnce() -> R, R: Display,

Implementors