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§
1.0.0 · 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);
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.
Implementors§
source§impl FromStr for ClientCachePreference
impl FromStr for ClientCachePreference
type Err = CachePreferenceError
source§impl FromStr for ServerCachePreference
impl FromStr for ServerCachePreference
type Err = CachePreferenceError
1.0.0 · source§impl FromStr for SocketAddr
impl FromStr for SocketAddr
type Err = AddrParseError
source§impl FromStr for log::LevelFilter
impl FromStr for log::LevelFilter
type Err = ParseLevelError
§impl FromStr for CompactString
impl FromStr for CompactString
type Err = Infallible
§impl FromStr for HeaderName
impl FromStr for HeaderName
type Err = InvalidHeaderName
§impl FromStr for HeaderValue
impl FromStr for HeaderValue
type Err = InvalidHeaderValue
§impl FromStr for StatusCode
impl FromStr for StatusCode
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
§impl FromStr for PathAndQuery
impl FromStr for PathAndQuery
type Err = InvalidUri
1.0.0 · source§impl FromStr for String
Available on non-no_global_oom_handling
only.
impl FromStr for String
no_global_oom_handling
only.