Struct rocket::Catcher[][src]

pub struct Catcher {
    pub name: Option<Cow<'static, str>>,
    pub base: Origin<'static>,
    pub code: Option<u16>,
    pub handler: Box<dyn Handler>,
}
Expand description

An error catching route.

Catchers are routes that run when errors are produced by the application. They consist of a Handler and an optional status code to match against arising errors. Errors arise from the the following sources:

  • A failing guard.
  • A failing responder.
  • Routing failure.

Each failure is paired with a status code. Guards and responders indicate the status code themselves via their Err return value while a routing failure is always a 404. Rocket invokes the error handler for the catcher with the error’s status code.

Error Handler Restrictions

Because error handlers are a last resort, they should not fail to produce a response. If an error handler does fail, Rocket invokes its default 500 error catcher. Error handlers cannot forward.

Routing

An error arising from a particular request matches a catcher iff:

  • It is a default catcher or has a status code matching the error code.
  • Its base is a prefix of the normalized/decoded request URI path.

A default catcher is a catcher with no explicit status code: None. The catcher’s base is provided as the first argument to Rocket::register().

Collisions

Two catchers are said to collide if there exists an error that matches both catchers. Colliding catchers present a routing ambiguity and are thus disallowed by Rocket. Because catchers can be constructed dynamically, collision checking is done at ignite time, after it becomes statically impossible to register any more catchers on an instance of Rocket.

Built-In Default

Rocket’s provides a built-in default catcher that can handle all errors. It produces HTML or JSON, depending on the value of the Accept header. As such, catchers only need to be registered if an error needs to be handled in a custom fashion. The built-in default never conflicts with any user-registered catchers.

Code Generation

Catchers should rarely be constructed or used directly. Instead, they are typically generated via the catch attribute, as follows:

#[macro_use] extern crate rocket;

use rocket::Request;
use rocket::http::Status;

#[catch(500)]
fn internal_error() -> &'static str {
    "Whoops! Looks like we messed up."
}

#[catch(404)]
fn not_found(req: &Request) -> String {
    format!("I couldn't find '{}'. Try something else?", req.uri())
}

#[catch(default)]
fn default(status: Status, req: &Request) -> String {
    format!("{} ({})", status, req.uri())
}

#[launch]
fn rocket() -> _ {
    rocket::build().register("/", catchers![internal_error, not_found, default])
}

A function decorated with #[catch] may take zero, one, or two arguments. It’s type signature must be one of the following, where R:Responder:

See the catch documentation for full details.

Fields

name: Option<Cow<'static, str>>

The name of this catcher, if one was given.

base: Origin<'static>

The mount point.

code: Option<u16>

The HTTP status to match against if this route is not default.

handler: Box<dyn Handler>

The catcher’s associated error handler.

Implementations

impl Catcher[src]

pub fn new<S, H>(code: S, handler: H) -> Catcher where
    S: Into<Option<u16>>,
    H: Handler
[src]

Creates a catcher for the given status, or a default catcher if status is None, using the given error handler. This should only be used when routing manually.

Examples

use rocket::request::Request;
use rocket::catcher::{Catcher, BoxFuture};
use rocket::response::Responder;
use rocket::http::Status;

fn handle_404<'r>(status: Status, req: &'r Request<'_>) -> BoxFuture<'r> {
   let res = (status, format!("404: {}", req.uri()));
   Box::pin(async move { res.respond_to(req) })
}

fn handle_500<'r>(_: Status, req: &'r Request<'_>) -> BoxFuture<'r> {
    Box::pin(async move{ "Whoops, we messed up!".respond_to(req) })
}

fn handle_default<'r>(status: Status, req: &'r Request<'_>) -> BoxFuture<'r> {
   let res = (status, format!("{}: {}", status, req.uri()));
   Box::pin(async move { res.respond_to(req) })
}

let not_found_catcher = Catcher::new(404, handle_404);
let internal_server_error_catcher = Catcher::new(500, handle_500);
let default_error_catcher = Catcher::new(None, handle_default);

Panics

Panics if code is not in the HTTP status code error range [400, 600).

pub fn map_base<'a, F>(self, mapper: F) -> Result<Self, Error<'static>> where
    F: FnOnce(Origin<'a>) -> String
[src]

Maps the base of this catcher using mapper, returning a new Catcher with the returned base.

mapper is called with the current base. The returned String is used as the new base if it is a valid URI. If the returned base URI contains a query, it is ignored. Returns an error if the base produced by mapper is not a valid origin URI.

Example

use rocket::request::Request;
use rocket::catcher::{Catcher, BoxFuture};
use rocket::response::Responder;
use rocket::http::Status;

fn handle_404<'r>(status: Status, req: &'r Request<'_>) -> BoxFuture<'r> {
   let res = (status, format!("404: {}", req.uri()));
   Box::pin(async move { res.respond_to(req) })
}

let catcher = Catcher::new(404, handle_404);
assert_eq!(catcher.base.path(), "/");

let catcher = catcher.map_base(|_| format!("/bar")).unwrap();
assert_eq!(catcher.base.path(), "/bar");

let catcher = catcher.map_base(|base| format!("/foo{}", base)).unwrap();
assert_eq!(catcher.base.path(), "/foo/bar");

let catcher = catcher.map_base(|base| format!("/foo ? {}", base));
assert!(catcher.is_err());

Trait Implementations

impl Clone for Catcher[src]

fn clone(&self) -> Catcher[src]

Returns a copy of the value. Read more

fn clone_from(&mut self, source: &Self)1.0.0[src]

Performs copy-assignment from source. Read more

impl Debug for Catcher[src]

fn fmt(&self, f: &mut Formatter<'_>) -> Result[src]

Formats the value using the given formatter. Read more

impl Default for Catcher[src]

fn default() -> Self[src]

Returns the “default value” for a type. Read more

impl Display for Catcher[src]

fn fmt(&self, f: &mut Formatter<'_>) -> Result[src]

Formats the value using the given formatter. Read more

Auto Trait Implementations

impl !RefUnwindSafe for Catcher

impl Send for Catcher

impl Sync for Catcher

impl Unpin for Catcher

impl !UnwindSafe for Catcher

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
[src]

pub fn type_id(&self) -> TypeId[src]

Gets the TypeId of self. Read more

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

pub fn borrow(&self) -> &T[src]

Immutably borrows from an owned value. Read more

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

pub fn borrow_mut(&mut self) -> &mut T[src]

Mutably borrows from an owned value. Read more

impl<T> From<T> for T[src]

pub fn from(t: T) -> T[src]

Performs the conversion.

impl<T> Instrument for T[src]

fn instrument(self, span: Span) -> Instrumented<Self>[src]

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more

fn in_current_span(self) -> Instrumented<Self>[src]

Instruments this type with the current Span, returning an Instrumented wrapper. Read more

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

pub fn into(self) -> U[src]

Performs the conversion.

impl<T> IntoCollection<T> for T

pub fn into_collection<A>(self) -> SmallVec<A> where
    A: Array<Item = T>, 

Converts self into a collection.

pub fn mapped<U, F, A>(self, f: F) -> SmallVec<A> where
    F: FnMut(T) -> U,
    A: Array<Item = U>, 

impl<T> Same<T> for T

type Output = T

Should always be Self

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

pub fn to_owned(&self) -> T[src]

Creates owned data from borrowed data, usually by cloning. Read more

pub fn clone_into(&self, target: &mut T)[src]

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

impl<T> ToString for T where
    T: Display + ?Sized
[src]

pub default fn to_string(&self) -> String[src]

Converts the given value to a String. Read more

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>[src]

Performs the conversion.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>[src]

Performs the conversion.

impl<V, T> VZip<V> for T where
    V: MultiLane<T>, 

pub fn vzip(self) -> V