Struct mycelium_util::fmt::FmtOption

pub struct FmtOption<'a, T> { /* private fields */ }

A utility to assist with formatting Option values.

This wraps a reference to an Option value, and implements formatting traits by formatting the Option’s contents if it is Some. If the Option is None, the formatting trait implementations emit no text by default, or a string provided using the or_else method.

A FmtOption will implement the core::fmt::Display, core::fmt::Debug, core::fmt::Binary, core::fmt::UpperHex, core::fmt::LowerHex, and core::fmt::Pointer formatting traits, if the inner type implements the corresponding trait.

The fmt::opt method can be used as shorthand to borrow an Option as a FmtOption.

Examples

Formatting a Some value emits that value’s Debug and Display output:

use mycelium_util::fmt;

let value = Some("hello world");
let debug = format!("{:?}", fmt::opt(&value));
assert_eq!(debug, "\"hello world\"");

let display = format!("{}", fmt::opt(&value));
assert_eq!(display, "hello world");

Formatting a None value generates no text by default:

use mycelium_util::fmt;

let value: Option<&str> = None;
let debug = format!("{:?}", fmt::opt(&value));
assert_eq!(debug, "");

let display = format!("{}", fmt::opt(&value));
assert_eq!(display, "");

The or_else method can be used to customize the text that is emitted when the value is None:

use mycelium_util::fmt;
use core::ptr::NonNull;

let value: Option<NonNull<u8>> = None;
let debug = format!("{:?}", fmt::opt(&value).or_else("null"));
assert_eq!(debug, "null");

Implementations

impl<'a, T> FmtOption<'a, T>

pub const fn new(opt: &'a Option<T>) -> Self

Returns a new FmtOption that formats the provided Option value.

The fmt::opt function can be used as shorthand for this.

pub fn or_else(self, or_else: &'a str) -> Self

Set the text to emit when the value is None.

Examples

If the value is None, the or_else text is emitted:

use mycelium_util::fmt;
use core::ptr::NonNull;

let value: Option<NonNull<u8>> = None;
let debug = format!("{:?}", fmt::opt(&value).or_else("null"));
assert_eq!(debug, "null");

If the value is Some, this function does nothing:

let value = Some("hello world");
let debug = format!("{}", fmt::opt(&value).or_else("no string"));
assert_eq!(debug, "hello world");

Trait Implementations

impl<T: Binary> Binary for FmtOption<'_, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a, T: Clone> Clone for FmtOption<'a, T>

fn clone(&self) -> FmtOption<'a, T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for FmtOption<'_, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Display> Display for FmtOption<'_, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: LowerHex> LowerHex for FmtOption<'_, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Pointer> Pointer for FmtOption<'_, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: UpperHex> UpperHex for FmtOption<'_, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.