pub(crate) 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
.
§Input format and round-tripping
The input format expected by a type’s FromStr
implementation depends on the type. Check the
type’s documentation for the input formats it knows how to parse. Note that the input format of
a type’s FromStr
implementation might not necessarily accept the output format of its
Display
implementation, and even if it does, the Display
implementation may not be lossless
so the round-trip may lose information.
However, if a type has a lossless Display
implementation whose output is meant to be
conveniently machine-parseable and not just meant for human consumption, then the type may wish
to accept the same format in FromStr
, and document that usage. Having both Display
and
FromStr
implementations where the result of Display
cannot be parsed with FromStr
may
surprise users.
§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 tor_general_addr::general::SocketAddr
impl FromStr for tor_general_addr::general::SocketAddr
type Err = AddrParseError
Source§impl FromStr for RelayIdType
impl FromStr for RelayIdType
type Err = RelayIdError
Source§impl FromStr for PtTargetAddr
impl FromStr for PtTargetAddr
type Err = BridgeAddrError
1.0.0 · Source§impl FromStr for core::net::socket_addr::SocketAddr
impl FromStr for core::net::socket_addr::SocketAddr
type Err = AddrParseError
Source§impl FromStr for log::LevelFilter
impl FromStr for log::LevelFilter
type Err = ParseLevelError
Source§impl FromStr for BridgeConfig
impl FromStr for BridgeConfig
type Err = BridgeParseError
Source§impl FromStr for BridgeConfigBuilder
BridgeConfigBuilder
parses the same way as BridgeConfig
impl FromStr for BridgeConfigBuilder
BridgeConfigBuilder
parses the same way as BridgeConfig
type Err = BridgeParseError
Source§impl FromStr for BridgeAddr
impl FromStr for BridgeAddr
type Err = BridgeAddrError
Source§impl FromStr for PtTransportName
impl FromStr for PtTransportName
type Err = TransportIdError
Source§impl FromStr for TransportId
impl FromStr for TransportId
type Err = TransportIdError
Source§impl FromStr for AddrPortPattern
impl FromStr for AddrPortPattern
type Err = PolicyError
Source§impl FromStr for PortPolicy
impl FromStr for PortPolicy
type Err = PolicyError
Source§impl FromStr for Iso8601TimeSlug
impl FromStr for Iso8601TimeSlug
type Err = BadIso8601TimeSlug
Source§impl FromStr for Protocols
A Protocols set can be parsed from a string according to the
format used in Tor consensus documents.
impl FromStr for Protocols
A Protocols set can be parsed from a string according to the format used in Tor consensus documents.
A protocols set is represented by a space-separated list of
entries. Each entry is of the form Name=Versions
, where Name
is the name of a protocol, and Versions
is a comma-separated
list of version numbers and version ranges. Each version range is
a pair of integers separated by -
.
No protocol name may be listed twice. No version may be listed twice for a single protocol. All versions must be in range 0 through 63 inclusive.
type Err = ParseError
Source§impl FromStr for HsClientNickname
Available on crate feature restricted-discovery
only.
impl FromStr for HsClientNickname
restricted-discovery
only.Source§impl FromStr for IptLocalId
impl FromStr for IptLocalId
type Err = InvalidIptLocalId
Source§impl FromStr for HsNickname
impl FromStr for HsNickname
type Err = InvalidNickname
Source§impl FromStr for FutureTimestamp
impl FromStr for FutureTimestamp
type Err = ParseError
Source§impl FromStr for ByteString
impl FromStr for ByteString
type Err = Infallible
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
Source§impl FromStr for Url
Parse a string as an URL, without a base URL or encoding override.
impl FromStr for Url
Parse a string as an URL, without a base URL or encoding override.
type Err = ParseError
Source§impl FromStr for HsClientDescEncKey
impl FromStr for HsClientDescEncKey
1.32.0 · Source§impl FromStr for tor_hsservice::internal_prelude::PathBuf
impl FromStr for tor_hsservice::internal_prelude::PathBuf
type Err = Infallible
§impl FromStr for InternalString
impl FromStr for InternalString
type Err = Infallible
§impl FromStr for Num
impl FromStr for Num
type Err = Either<ParseIntError, ParseFloatError>
§impl FromStr for PathBuf
impl FromStr for PathBuf
type Err = Infallible
§impl FromStr for Signature
Decode a signature from hexadecimal.
impl FromStr for Signature
Decode a signature from hexadecimal.
Upper and lower case hexadecimal are both accepted, however mixed case is rejected.
§impl FromStr for u1
impl FromStr for u1
type Err = ParseIntError
§impl FromStr for u2
impl FromStr for u2
type Err = ParseIntError
§impl FromStr for u3
impl FromStr for u3
type Err = ParseIntError
§impl FromStr for u4
impl FromStr for u4
type Err = ParseIntError
§impl FromStr for u5
impl FromStr for u5
type Err = ParseIntError
§impl FromStr for u6
impl FromStr for u6
type Err = ParseIntError
§impl FromStr for u7
impl FromStr for u7
type Err = ParseIntError
§impl FromStr for u24
impl FromStr for u24
type Err = ParseIntError
§impl FromStr for u40
impl FromStr for u40
type Err = ParseIntError
§impl FromStr for u48
impl FromStr for u48
type Err = ParseIntError
§impl FromStr for u56
impl FromStr for u56
type Err = ParseIntError
§impl<Size> FromStr for EncodedPoint<Size>where
Size: ModulusSize,
Decode a SEC1-encoded point from hexadecimal.
impl<Size> FromStr for EncodedPoint<Size>where
Size: ModulusSize,
Decode a SEC1-encoded point from hexadecimal.
Upper and lower case hexadecimal are both accepted, however mixed case is rejected.