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Document outcome module.

This commit is contained in:
Sergio Benitez 2016-10-19 00:30:02 -07:00
parent 2a0535e1f7
commit 81f45608a1
1 changed files with 228 additions and 1 deletions
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lib/src/outcome.rs
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@ -1,10 +1,94 @@
//! Success, failure, and forward handling.
//!
//! The `Outcome<S, E, F>` type is similar to the standard library's `Result<S,
//! E>` type. It is an enum with three variants, each containing a value:
//! `Success(S)`, which represents a successful outcome, `Failure(E)`, which
//! represents a failing outcome, and `Forward(F)`, which represents neither a
//! success or failure, but instead, indicates that processing could not be
//! handled and should instead be _forwarded_ to whatever can handle the
//! processing next.
//!
//! The `Outcome` type is the return type of many of the core Rocket traits,
//! including [FromRequest](../request/trait.FromRequest.html),
//! [FromData](../request/trait.FromData.html), and
//! [Responder](../response/trait.Responder.html). It is also the return type of
//! request handlers via the [Response](../response/type.Response.html) type
//! alias.
//!
//! # Success
//!
//! A successful `Outcome<S, E, F>`, `Success(S)`, is returned from functions
//! that complete successfully. The meaning of a `Success` outcome depends on
//! the context. For instance, the `Outcome` of the `from_data` method of the
//! `FromData` trait will be matched against the type expected by the user. For
//! example, consider the following handler:
//!
//! ```rust,ignore
//! #[post("/", data = "<my_val>")]
//! fn hello(my_val: S) -> ... { }
//! ```
//!
//! The `FromData` implementation for the type `S` returns an `Outcome` with a
//! `Success(S)`. If `from_data` returns a `Success`, the `Success` value will
//! be unwrapped and the value will be used as the value of `my_val`.
//!
//! # Failure
//!
//! A failure `Outcome<S, E, F>`, `Failure(E)`, is returned when a function
//! fails with some error and no processing can or should continue as a result.
//! The meaning of a failure depends on the context.
//!
//! It Rocket, a `Failure` generally means that a request is taken out of normal
//! processing. The request is then given to the catcher corresponding to some
//! status code. users can catch failures by requesting a type of `Result<S, E>`
//! or `Option<S>` in request handlers. For example, if a user's handler looks
//! like:
//!
//! ```rust,ignore
//! #[post("/", data = "<my_val>")]
//! fn hello(my_val: Result<S, E>) -> ... { }
//! ```
//!
//! The `FromData` implementation for the type `S` returns an `Outcome` with a
//! `Success(S)` and `Failure(E)`. If `from_data` returns a `Failure`, the
//! `Failure` value will be unwrapped and the value will be used as the `Err`
//! value of `my_val` while a `Success` will be unwrapped and used the `Ok`
//! value.
//!
//! # Forward
//!
//! A forward `Outcome<S, E, F>`, `Forward(F)`, is returned when a function
//! wants to indicate that the requested processing should be _forwarded_ to the
//! next available processor. Again, the exact meaning depends on the context.
//!
//! In Rocket, a `Forward` generally means that a request is forwarded to the
//! next available request handler. For example, consider the following request
//! handler:
//!
//! ```rust,ignore
//! #[post("/", data = "<my_val>")]
//! fn hello(my_val: S) -> ... { }
//! ```
//!
//! The `FromData` implementation for the type `S` returns an `Outcome` with a
//! `Success(S)`, `Failure(E)`, and `Forward(F)`. If the `Outcome` is a
//! `Forward`, the `hello` handler isn't called. Instead, the incoming request
//! is forwarded, or passed on to, the next matching route, if any. Ultimately,
//! if there are no non-forwarding routes, forwarded requests are handled by the
//! 404 catcher. Similar to `Failure`s, users can catch `Forward`s by requesting
//! a type of `Option<S>`. If an `Outcome` is a `Forward`, the `Option` will be
//! `None`.
use std::fmt;
use term_painter::Color::*;
use term_painter::Color;
use term_painter::ToStyle;
/// An enum representing success (`Success`), failure (`Failure`), or
/// forwarding (`Forward`).
#[must_use]
#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash)]
pub enum Outcome<S, E, F> {
/// Contains the success value.
Success(S),
@ -19,7 +103,17 @@ impl<S, E, F> Outcome<S, E, F> {
///
/// # Panics
///
/// Panics if the value is not Success.
/// Panics if the value is not `Success`.
///
/// # Examples
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let x: Outcome<i32, &str, usize> = Success(10);
/// assert_eq!(x.unwrap(), 10);
/// ```
#[inline(always)]
pub fn unwrap(self) -> S {
match self {
@ -29,6 +123,22 @@ impl<S, E, F> Outcome<S, E, F> {
}
/// Return true if this `Outcome` is a `Success`.
///
/// # Examples
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let x: Outcome<i32, &str, usize> = Success(10);
/// assert_eq!(x.is_success(), true);
///
/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
/// assert_eq!(x.is_success(), false);
///
/// let x: Outcome<i32, &str, usize> = Forward(25);
/// assert_eq!(x.is_success(), false);
/// ```
#[inline(always)]
pub fn is_success(&self) -> bool {
match *self {
@ -38,6 +148,22 @@ impl<S, E, F> Outcome<S, E, F> {
}
/// Return true if this `Outcome` is a `Failure`.
///
/// # Examples
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let x: Outcome<i32, &str, usize> = Success(10);
/// assert_eq!(x.is_failure(), false);
///
/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
/// assert_eq!(x.is_failure(), true);
///
/// let x: Outcome<i32, &str, usize> = Forward(25);
/// assert_eq!(x.is_failure(), false);
/// ```
#[inline(always)]
pub fn is_failure(&self) -> bool {
match *self {
@ -47,6 +173,22 @@ impl<S, E, F> Outcome<S, E, F> {
}
/// Return true if this `Outcome` is a `Forward`.
///
/// # Examples
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let x: Outcome<i32, &str, usize> = Success(10);
/// assert_eq!(x.is_forward(), false);
///
/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
/// assert_eq!(x.is_forward(), false);
///
/// let x: Outcome<i32, &str, usize> = Forward(25);
/// assert_eq!(x.is_forward(), true);
/// ```
#[inline(always)]
pub fn is_forward(&self) -> bool {
match *self {
@ -59,6 +201,20 @@ impl<S, E, F> Outcome<S, E, F> {
///
/// Returns the `Some` of the `Success` if this is a `Success`, otherwise
/// returns `None`. `self` is consumed, and all other values are discarded.
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let x: Outcome<i32, &str, usize> = Success(10);
/// assert_eq!(x.succeeded(), Some(10));
///
/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
/// assert_eq!(x.succeeded(), None);
///
/// let x: Outcome<i32, &str, usize> = Forward(25);
/// assert_eq!(x.succeeded(), None);
/// ```
#[inline(always)]
pub fn succeeded(self) -> Option<S> {
match self {
@ -71,6 +227,20 @@ impl<S, E, F> Outcome<S, E, F> {
///
/// Returns the `Some` of the `Failure` if this is a `Failure`, otherwise
/// returns `None`. `self` is consumed, and all other values are discarded.
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let x: Outcome<i32, &str, usize> = Success(10);
/// assert_eq!(x.failed(), None);
///
/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
/// assert_eq!(x.failed(), Some("Hi! I'm an error."));
///
/// let x: Outcome<i32, &str, usize> = Forward(25);
/// assert_eq!(x.failed(), None);
/// ```
#[inline(always)]
pub fn failed(self) -> Option<E> {
match self {
@ -83,6 +253,20 @@ impl<S, E, F> Outcome<S, E, F> {
///
/// Returns the `Some` of the `Forward` if this is a `Forward`, otherwise
/// returns `None`. `self` is consumed, and all other values are discarded.
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let x: Outcome<i32, &str, usize> = Success(10);
/// assert_eq!(x.forwarded(), None);
///
/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
/// assert_eq!(x.forwarded(), None);
///
/// let x: Outcome<i32, &str, usize> = Forward(25);
/// assert_eq!(x.forwarded(), Some(25));
/// ```
#[inline(always)]
pub fn forwarded(self) -> Option<F> {
match self {
@ -91,6 +275,49 @@ impl<S, E, F> Outcome<S, E, F> {
}
}
/// Converts from `Outcome<S, E, F>` to `Outcome<&S, &E, &F>`.
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let x: Outcome<i32, &str, usize> = Success(10);
/// assert_eq!(x.as_ref(), Success(&10));
///
/// let x: Outcome<i32, &str, usize> = Failure("Hi! I'm an error.");
/// assert_eq!(x.as_ref(), Failure(&"Hi! I'm an error."));
/// ```
#[inline(always)]
pub fn as_ref(&self) -> Outcome<&S, &E, &F> {
match *self {
Outcome::Success(ref val) => Outcome::Success(val),
Outcome::Failure(ref val) => Outcome::Failure(val),
Outcome::Forward(ref val) => Outcome::Forward(val),
}
}
/// Converts from `Outcome<S, E, F>` to `Outcome<&mut S, &mut E, &mut F>`.
///
/// ```rust
/// # use rocket::outcome::Outcome;
/// # use rocket::outcome::Outcome::*;
/// #
/// let mut x: Outcome<i32, &str, usize> = Success(10);
/// if let Success(val) = x.as_mut() {
/// *val = 20;
/// }
///
/// assert_eq!(x.unwrap(), 20);
/// ```
#[inline(always)]
pub fn as_mut(&mut self) -> Outcome<&mut S, &mut E, &mut F> {
match *self {
Outcome::Success(ref mut val) => Outcome::Success(val),
Outcome::Failure(ref mut val) => Outcome::Failure(val),
Outcome::Forward(ref mut val) => Outcome::Forward(val),
}
}
#[inline(always)]
fn formatting(&self) -> (Color, &'static str) {
match *self {