Trait devela::_libstd::str::FromStr

1.0.0 · source ·

pub trait FromStr: Sized {
    type Err;

    // Required method
    fn from_str(s: &str) -> Result<Self, Self::Err>;
}

Expand description

Parse a value from a string

FromStr’s from_str method is often used implicitly, through str’s parse method. See parse’s documentation for examples.

FromStr does not have a lifetime parameter, and so you can only parse types that do not contain a lifetime parameter themselves. In other words, you can parse an i32 with FromStr, but not a &i32. You can parse a struct that contains an i32, but not one that contains an &i32.

§Examples

Basic implementation of FromStr on an example Point type:

use std::str::FromStr;

#[derive(Debug, PartialEq)]
struct Point {
    x: i32,
    y: i32
}

#[derive(Debug, PartialEq, Eq)]
struct ParsePointError;

impl FromStr for Point {
    type Err = ParsePointError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let (x, y) = s
            .strip_prefix('(')
            .and_then(|s| s.strip_suffix(')'))
            .and_then(|s| s.split_once(','))
            .ok_or(ParsePointError)?;

        let x_fromstr = x.parse::<i32>().map_err(|_| ParsePointError)?;
        let y_fromstr = y.parse::<i32>().map_err(|_| ParsePointError)?;

        Ok(Point { x: x_fromstr, y: y_fromstr })
    }
}

let expected = Ok(Point { x: 1, y: 2 });
// Explicit call
assert_eq!(Point::from_str("(1,2)"), expected);
// Implicit calls, through parse
assert_eq!("(1,2)".parse(), expected);
assert_eq!("(1,2)".parse::<Point>(), expected);
// Invalid input string
assert!(Point::from_str("(1 2)").is_err());

Required Associated Types§

1.0.0 · source

type Err

The associated error which can be returned from parsing.

Required Methods§

1.0.0 · source

fn from_str(s: &str) -> Result<Self, Self::Err>

Parses a string s to return a value of this type.

If parsing succeeds, return the value inside Ok, otherwise when the string is ill-formatted return an error specific to the inside Err. The error type is specific to the implementation of the trait.

§Examples

Basic usage with i32, a type that implements FromStr:

use std::str::FromStr;

let s = "5";
let x = i32::from_str(s).unwrap();

assert_eq!(5, x);

Object Safety§

This trait is not object safe.

Implementors§

source §

impl FromStr for Month

Returns a Month from a string containing either the full month name, or any of the month ASCII abbreviations.

§

type Err = &'static str

source §

impl FromStr for Weekday

Returns a Weekday from a string containing either the full weekday name, or any of the weekday ASCII abbreviations.

type Err

Required Methods§

fn from_str(s: &str) -> Result<Self, Self::Err>

§Examples

Object Safety§

Implementors§

impl FromStr for Level

type Err = ParseLevelError

impl FromStr for LevelFilter

type Err = ParseLevelError

impl FromStr for Month

type Err = &'static str

impl FromStr for Weekday

type Err = &'static str

impl FromStr for IpAddr

type Err = AddrParseError

impl FromStr for SocketAddr

type Err = AddrParseError

impl FromStr for bool

type Err = ParseBoolError

impl FromStr for char

type Err = ParseCharError

impl FromStr for f32

type Err = ParseFloatError

impl FromStr for f64

type Err = ParseFloatError

impl FromStr for i8

type Err = ParseIntError

impl FromStr for i16

type Err = ParseIntError

impl FromStr for i32

type Err = ParseIntError

impl FromStr for i64

type Err = ParseIntError

impl FromStr for i128

type Err = ParseIntError

impl FromStr for isize

type Err = ParseIntError

impl FromStr for u8

type Err = ParseIntError

impl FromStr for u16

type Err = ParseIntError

impl FromStr for u32

type Err = ParseIntError

impl FromStr for u64

type Err = ParseIntError

impl FromStr for u128

type Err = ParseIntError

impl FromStr for usize

type Err = ParseIntError

impl FromStr for OsString

type Err = Infallible

impl FromStr for Ipv4Addr

type Err = AddrParseError

impl FromStr for Ipv6Addr

type Err = AddrParseError

impl FromStr for SocketAddrV4

type Err = AddrParseError

impl FromStr for SocketAddrV6

type Err = AddrParseError

impl FromStr for NonZero<i8>

type Err = ParseIntError

impl FromStr for NonZero<i16>

type Err = ParseIntError

impl FromStr for NonZero<i32>

type Err = ParseIntError

impl FromStr for NonZero<i64>

type Err = ParseIntError

impl FromStr for NonZero<i128>

type Err = ParseIntError

impl FromStr for NonZero<isize>

type Err = ParseIntError

impl FromStr for NonZero<u8>

type Err = ParseIntError

impl FromStr for NonZero<u16>

type Err = ParseIntError

impl FromStr for NonZero<u32>

Trait devela::_libstd::str::FromStr