Struct Catcher

pub struct Catcher {
    pub code: u16,
    pub handler: ErrorHandler,
    /* private fields */
}

An error catching route.

Catchers are routes that run when errors occur. They correspond directly with the HTTP error status code they will be handling and are registered with Rocket via Rocket::register(). For example, to handle “404 not found” errors, a catcher for the “404” status code is registered.

Because error handlers are only called when all routes are exhausted, they should not fail nor forward. If an error catcher fails, the user will receive no response. If an error catcher forwards, Rocket will respond with an internal server error.

Built-In Catchers

Rocket has many built-in, pre-registered default catchers. In particular, Rocket has catchers for all of the following status codes: 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 421, 426, 428, 429, 431, 451, 500, 501, 503, and 510. As such, catchers only need to be registered if an error needs to be handled in a custom fashion.

Code Generation

Catchers should rarely be used directly. Instead, they are typically declared using the catch decorator, as follows:

#![feature(proc_macro_hygiene, decl_macro)]

#[macro_use] extern crate rocket;

use rocket::Request;

#[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())
}

fn main() {
    rocket::ignite().register(catchers![internal_error, not_found]).launch();
}

A function decorated with catch must take exactly zero or one arguments. If the catcher takes an argument, it must be of type &Request.

Fields

code: u16

The HTTP status code to match against.

handler: ErrorHandler

The catcher’s associated handler.

Implementations

impl Catcher

pub fn new(code: u16, handler: ErrorHandler) -> Catcher

Creates a catcher for the given status code using the given error handler. This should only be used when routing manually.

Examples

use rocket::{Catcher, Request};
use rocket::response::{Result, Responder};
use rocket::response::status::Custom;
use rocket::http::Status;

fn handle_404<'r>(req: &'r Request) -> Result<'r> {
    let res = Custom(Status::NotFound, format!("404: {}", req.uri()));
    res.respond_to(req)
}

fn handle_500<'r>(req: &'r Request) -> Result<'r> {
    "Whoops, we messed up!".respond_to(req)
}

let not_found_catcher = Catcher::new(404, handle_404);
let internal_server_error_catcher = Catcher::new(500, handle_500);

Trait Implementations

impl Display for Catcher

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

Formats the value using the given formatter.