Trait OptionExt

pub trait OptionExt<T> {
    // Required methods
    fn contains<U>(&self, x: &U) -> bool
       where U: PartialEq<T>;
    fn map_or2<U, F: FnOnce(T) -> U>(self, f: F, default: U) -> U;
    fn map_or_else2<U, F: FnOnce(T) -> U, D: FnOnce() -> U>(
        self,
        f: F,
        default: D,
    ) -> U;
}

Extension trait providing additional methods for Option.

Required Methods

fn contains<U>(&self, x: &U) -> bool

where U: PartialEq<T>,

Returns true if the option is a Some value containing the given value.

Examples

use option_ext::OptionExt;

let x: Option<u32> = Some(2);
assert_eq!(x.contains(&2), true);

let x: Option<u32> = Some(3);
assert_eq!(x.contains(&2), false);

let x: Option<u32> = None;
assert_eq!(x.contains(&2), false);

fn map_or2<U, F: FnOnce(T) -> U>(self, f: F, default: U) -> U

Returns the result from applying the function to the contained value if the option is Some, or returns provided default result if the option is None.

The f argument of map_or2 is only evaluated if the option is Some. The default argument of map_or2 is always evaluated – even if the option is Some. Use map_or_else2 to avoid this.

Examples

use option_ext::OptionExt;

let x = Some("bar");
assert_eq!(x.map_or2(|v| v.len(), 42), 3);

let x: Option<&str> = None;
assert_eq!(x.map_or2(|v| v.len(), 42), 42);

fn map_or_else2<U, F: FnOnce(T) -> U, D: FnOnce() -> U>( self, f: F, default: D, ) -> U

Returns the result from applying the function to the contained value if the option is Some, or returns the result from evaluating the provided default function if the option is None.

The f argument of map_or_else2 is only evaluated if the option is Some. The default argument of map_or_else2 is only evaluated if the option is None. Use map_or2 to always evaluate the default argument.

Examples

use option_ext::OptionExt;

let k = 23;

let x = Some("bar");
assert_eq!(x.map_or_else2(|v| v.len(), || 2 * k), 3);

let x: Option<&str> = None;
assert_eq!(x.map_or_else2(|v| v.len(), || 2 * k), 46);

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 contains<U>(&self, x: &U) -> bool

where U: PartialEq<T>,

fn map_or2<U, F: FnOnce(T) -> U>(self, f: F, default: U) -> U

fn map_or_else2<U, F: FnOnce(T) -> U, D: FnOnce() -> U>( self, f: F, default: D, ) -> U

Implementors