Trait OptionExt

pub trait OptionExt<T> {
    // Required methods
    fn err_or<U>(self, ok: U) -> Result<U, T>;
    fn err_or_else<U>(self, f: impl FnOnce() -> U) -> Result<U, T>;
    fn err_or_default<U: Default>(self) -> Result<U, T>;
    fn is_none_or(&self, f: impl FnOnce(&T) -> bool) -> bool;
    fn expect_none(self, msg: &str);
    fn tap_mut(self, f: impl FnOnce(&mut T)) -> Option<T>;
}

Extension methods for std::option::Option.

Required Methods

fn err_or<U>(self, ok: U) -> Result<U, T>

Converts an Option to a Result.

Unlike the standard library, the value of Option is treated as Result::Err instead of Result::Ok.

Arguments passed to err_or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use OptionExt::err_or_else, which is lazily evaluated.

Example

use rs_std_ext::option::OptionExt;
 
assert_eq!(Some("err").err_or(0), Err("err"));
assert_eq!(None::<&str>.err_or(0), Ok(0));

fn err_or_else<U>(self, f: impl FnOnce() -> U) -> Result<U, T>

Converts an Option to a Result.

Unlike the standard library, the value of Option is treated as Result::Err instead of Result::Ok.

Example

use rs_std_ext::option::OptionExt;
 
assert_eq!(Some("err").err_or_else(|| 0), Err("err"));
assert_eq!(None::<&str>.err_or_else(|| 0), Ok(0));

fn err_or_default<U: Default>(self) -> Result<U, T>

Converts an Option to a Result.

Unlike the standard library, the value of Option is treated as Result::Err instead of Result::Ok.

Example

use rs_std_ext::option::OptionExt;
 
assert_eq!(Some("err").err_or_default::<usize>(), Err("err"));
assert_eq!(None::<&str>.err_or_default::<usize>(), Ok(0));

fn is_none_or(&self, f: impl FnOnce(&T) -> bool) -> bool

👎Deprecated: Use Option::is_none_or (offered by std) instead.

Returns true if the Option is a None or the value inside of it matches a predicate.

This is equivalent to option.is_some_and(!f).

Example

use rs_std_ext::option::OptionExt;
 
assert_eq!(None::<usize>.is_none_or(|&i| i == 2), true);
assert_eq!(Some(5).is_none_or(|&i| i == 2), false);

fn expect_none(self, msg: &str)

Returns nothing, consuming the value contained.

Panics

Panics if the value is a Some with a custom panic message provided by msg.

Example

use rs_std_ext::option::OptionExt;
 
let x: Option<&str> = Some("10");
x.expect_none("fruits are healthy");// panics with `fruits are healthy`

Recommended Message Style

See the documentation for Option::expect for more information.

fn tap_mut(self, f: impl FnOnce(&mut T)) -> Option<T>

Tap into an Option and modify its value.

This method captures the Option in order not to break the caller-chain.

Example

use rs_std_ext::option::OptionExt;
 
let mut x: Option<String> = Some("4".into());
assert_eq!(x.tap_mut(|s| s.push('2')), Some("42".into()));

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 err_or<U>(self, ok: U) -> Result<U, T>

fn err_or_else<U>(self, f: impl FnOnce() -> U) -> Result<U, T>

fn err_or_default<U: Default>(self) -> Result<U, T>

fn is_none_or(&self, f: impl FnOnce(&T) -> bool) -> bool

👎Deprecated: Use Option::is_none_or (offered by std) instead.

fn expect_none(self, msg: &str)

fn tap_mut(self, f: impl FnOnce(&mut T)) -> Option<T>

Implementors