Trait rocket_http::uri::fmt::FromUriParam

source ·

pub trait FromUriParam<P: Part, T> {
    type Target: UriDisplay<P>;

    // Required method
    fn from_uri_param(param: T) -> Self::Target;
}

Expand description

Conversion trait for parameters used in uri! invocations.

Overview

In addition to implementing UriDisplay, to use a custom type in a uri! expression, the FromUriParam trait must be implemented. The UriDisplay derive automatically generates identity implementations of FromUriParam, so in the majority of cases, as with UriDisplay, this trait is never implemented manually.

In the rare case that UriDisplay is implemented manually, this trait, too, must be implemented explicitly. In the majority of cases, implementation can be automated. Rocket provides [impl_from_uri_param_identity] to generate the identity implementations automatically. For a type T, these are:

impl<P: Part> FromUriParam<P, T> for T
impl<'x, P: Part> FromUriParam<P, &'x T> for T
impl<'x, P: Part> FromUriParam<P, &'x mut T> for T

See impl_from_uri_param_identity! for usage details.

Code Generation

This trait is invoked once per expression passed into a uri! invocation. In particular, for a route URI parameter of type T and a user-supplied expression e of type S, <T as FromUriParam<S>>::from_uri_param(e) is invoked. The returned value of type T::Target is used in place of the user’s value and rendered using its UriDisplay implementation.

This trait allows types that differ from the route URI parameter’s types to be used in their place at no cost. For instance, the following implementation, provided by Rocket, allows an &str to be used in a uri! invocation for route URI parameters declared as String:

impl<'a, P: Part> FromUriParam<P, &'a str> for String {
    type Target = &'a str;
}

Because the FromUriParam::Target type is the same as the input type, the conversion is a no-op and free of cost, allowing an &str to be used in place of a String without penalty.

Provided Implementations

The following types have identity implementations:

String, i8, i16, i32, i64, i128, isize, u8, u16, u32, u64, u128, usize, f32, f64, bool, IpAddr, Ipv4Addr, Ipv6Addr, &str, Cow<str>

The following types have identity implementations only in Path:

&Path, PathBuf

The following types have identity implementations only in Query:

Option<T>, Result<T, E>

The following conversions are implemented for both paths and queries, allowing a value of the type on the left to be used when a type on the right is expected by a route:

&str to String
String to &str
T to Form<T>

The following conversions are implemented only in Path:

&str to &Path
&str to PathBuf
PathBuf to &Path
T to Option<T>
T to Result<T, E>

The following conversions are implemented only in Query:

Option<T> to Result<T, E> (for any E)
Result<T, E> to Option<T> (for any E)

See Foreign Impls for all provided implementations.

Implementing

This trait should only be implemented when you’d like to allow a type different from the route’s declared type to be used in its place in a uri! invocation. For instance, if the route has a type of T and you’d like to use a type of S in a uri! invocation, you’d implement FromUriParam<P, T> for S where P is Path for conversions valid in the path part of a URI, Uri for conversions valid in the query part of a URI, or P: Part when a conversion is valid in either case.

This is typically only warranted for owned-value types with corresponding reference types: String and &str, for instance. In this case, it’s desirable to allow an &str to be used in place of a String.

When implementing FromUriParam, be aware that Rocket will use the UriDisplay implementation of FromUriParam::Target, not of the source type. Incorrect implementations can result in creating unsafe URIs.

Example

The following example implements FromUriParam<Query, (&str, &str)> for a User type. The implementation allows an (&str, &str) type to be used in a uri! invocation where a User type is expected in the query part of the URI.

use std::fmt;

use rocket::http::uri::fmt::{Formatter, UriDisplay, FromUriParam, Query};

#[derive(FromForm)]
struct User<'a> {
    name: &'a str,
    nickname: String,
}

impl UriDisplay<Query> for User<'_> {
    fn fmt(&self, f: &mut Formatter<Query>) -> fmt::Result {
        f.write_named_value("name", &self.name)?;
        f.write_named_value("nickname", &self.nickname)
    }
}

impl<'a, 'b> FromUriParam<Query, (&'a str, &'b str)> for User<'a> {
    type Target = User<'a>;

    fn from_uri_param((name, nickname): (&'a str, &'b str)) -> User<'a> {
        User { name: name.into(), nickname: nickname.to_string() }
    }
}

With these implementations, the following typechecks:

#[post("/<name>?<user..>")]
fn some_route(name: &str, user: User<'_>)  { /* .. */ }

let uri = uri!(some_route(name = "hey", user = ("Robert Mike", "Bob")));
assert_eq!(uri.path(), "/hey");
assert_eq!(uri.query().unwrap(), "name=Robert%20Mike&nickname=Bob");

Required Associated Types§

source

type Target: UriDisplay<P>

The resulting type of this conversion.

Required Methods§

source

fn from_uri_param(param: T) -> Self::Target

Converts a value of type T into a value of type Self::Target. The resulting value of type Self::Target will be rendered into a URI using its UriDisplay implementation.

Trait rocket_http::uri::fmt::FromUriParam

Required Associated Types§

type Target: UriDisplay<P>

Required Methods§

fn from_uri_param(param: T) -> Self::Target

Implementations on Foreign Types§

impl<'a, P: Part> FromUriParam<P, String> for &'a str

type Target = String

fn from_uri_param(param: String) -> String

impl<A, E, T: FromUriParam<Query, A>> FromUriParam<Query, Result<A, E>> for Result<T, E>

type Target = Result<<T as FromUriParam<Query, A>>::Target, E>

fn from_uri_param(param: Result<A, E>) -> Self::Target

impl<P: Part> FromUriParam<P, u32> for u32

type Target = u32

fn from_uri_param(param: u32) -> u32

impl<P: Part> FromUriParam<P, Time> for Time

type Target = Time

fn from_uri_param(param: Time) -> Time

impl<'x, 'a> FromUriParam<Path, &'x &'a Path> for &'a Path

type Target = &'x &'a Path

fn from_uri_param(param: &'x &'a Path) -> &'x &'a Path

impl<'x, P: Part> FromUriParam<P, &'x mut u16> for u16

type Target = &'x mut u16

fn from_uri_param(param: &'x mut u16) -> &'x mut u16

impl<P: Part> FromUriParam<P, u8> for u8

type Target = u8

fn from_uri_param(param: u8) -> u8

impl<'x, P: Part> FromUriParam<P, &'x mut u128> for u128

type Target = &'x mut u128

fn from_uri_param(param: &'x mut u128) -> &'x mut u128

impl<'x, P: Part> FromUriParam<P, &'x i32> for i32

type Target = &'x i32

fn from_uri_param(param: &'x i32) -> &'x i32

impl<'x, P: Part> FromUriParam<P, &'x mut u64> for u64

type Target = &'x mut u64

fn from_uri_param(param: &'x mut u64) -> &'x mut u64

impl<P: Part> FromUriParam<P, NonZeroI128> for NonZeroI128

type Target = NonZeroI128

fn from_uri_param(param: NonZeroI128) -> NonZeroI128

impl<'x, P: Part> FromUriParam<P, &'x SocketAddr> for SocketAddr

type Target = &'x SocketAddr

fn from_uri_param(param: &'x SocketAddr) -> &'x SocketAddr

impl<'x, P: Part> FromUriParam<P, &'x mut NonZeroI32> for NonZeroI32

type Target = &'x mut NonZeroI32

fn from_uri_param(param: &'x mut NonZeroI32) -> &'x mut NonZeroI32

impl<'x, P: Part> FromUriParam<P, &'x NonZeroU32> for NonZeroU32

type Target = &'x NonZeroU32

fn from_uri_param(param: &'x NonZeroU32) -> &'x NonZeroU32

impl<P: Part> FromUriParam<P, NonZeroU8> for NonZeroU8

type Target = NonZeroU8

fn from_uri_param(param: NonZeroU8) -> NonZeroU8

impl<'a, P: Part> FromUriParam<P, Cow<'a, str>> for Cow<'a, str>

type Target = Cow<'a, str>

fn from_uri_param(param: Cow<'a, str>) -> Cow<'a, str>

impl<'x, P: Part> FromUriParam<P, &'x mut isize> for isize

type Target = &'x mut isize

fn from_uri_param(param: &'x mut isize) -> &'x mut isize

impl<'x, P: Part> FromUriParam<P, &'x PrimitiveDateTime> for PrimitiveDateTime

type Target = &'x PrimitiveDateTime

fn from_uri_param(param: &'x PrimitiveDateTime) -> &'x PrimitiveDateTime

impl<'x, P: Part> FromUriParam<P, &'x NonZeroI32> for NonZeroI32

type Target = &'x NonZeroI32

fn from_uri_param(param: &'x NonZeroI32) -> &'x NonZeroI32

impl<'x, P: Part> FromUriParam<P, &'x mut NonZeroI64> for NonZeroI64

type Target = &'x mut NonZeroI64

fn from_uri_param(param: &'x mut NonZeroI64) -> &'x mut NonZeroI64

impl<'x, P: Part> FromUriParam<P, &'x mut Ipv6Addr> for Ipv6Addr

type Target = &'x mut Ipv6Addr

fn from_uri_param(param: &'x mut Ipv6Addr) -> &'x mut Ipv6Addr

impl<'x, 'a> FromUriParam<Path, &'x mut &'a Path> for &'a Path

type Target = &'x mut &'a Path

fn from_uri_param(param: &'x mut &'a Path) -> &'x mut &'a Path

impl<'x, P: Part> FromUriParam<P, &'x mut u8> for u8

type Target = &'x mut u8

fn from_uri_param(param: &'x mut u8) -> &'x mut u8

impl<'x, P: Part> FromUriParam<P, &'x mut NonZeroIsize> for NonZeroIsize

type Target = &'x mut NonZeroIsize

fn from_uri_param(param: &'x mut NonZeroIsize) -> &'x mut NonZeroIsize

impl<P: Part> FromUriParam<P, usize> for usize

type Target = usize