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§
Required Methods§
sourcefn from_str(s: &str) -> Result<Self, Self::Err>
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§
Implementors§
source§impl FromStr for SocketAddr
impl FromStr for SocketAddr
type Err = AddrParseError
§impl FromStr for ChainId
impl FromStr for ChainId
Construct a ChainId from a string literal only if it forms a valid
identifier.
type Err = IdentifierError
§impl FromStr for ClientType
impl FromStr for ClientType
type Err = IdentifierError
§impl FromStr for ConnectionId
impl FromStr for ConnectionId
type Err = IdentifierError
1.5.0 · source§impl FromStr for SocketAddrV4
impl FromStr for SocketAddrV4
type Err = AddrParseError
1.5.0 · source§impl FromStr for SocketAddrV6
impl FromStr for SocketAddrV6
type Err = AddrParseError
1.35.0 · source§impl FromStr for NonZeroI16
impl FromStr for NonZeroI16
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroI32
impl FromStr for NonZeroI32
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroI64
impl FromStr for NonZeroI64
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroI128
impl FromStr for NonZeroI128
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroIsize
impl FromStr for NonZeroIsize
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroU16
impl FromStr for NonZeroU16
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroU32
impl FromStr for NonZeroU32
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroU64
impl FromStr for NonZeroU64
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroU128
impl FromStr for NonZeroU128
type Err = ParseIntError
1.35.0 · source§impl FromStr for NonZeroUsize
impl FromStr for NonZeroUsize
type Err = ParseIntError
§impl FromStr for Signature
impl FromStr for Signature
Decode a signature from hexadecimal.
Upper and lower case hexadecimal are both accepted, however mixed case is rejected.