[][src]Struct rocket::State

pub struct State<'r, T: Send + Sync + 'static>(_);

Request guard to retrieve managed state.

This type can be used as a request guard to retrieve the state Rocket is managing for some type T. This allows for the sharing of state across any number of handlers. A value for the given type must previously have been registered to be managed by Rocket via Rocket::manage(). The type being managed must be thread safe and sendable across thread boundaries. In other words, it must implement Send + Sync + 'static`.

Example

Imagine you have some configuration struct of the type MyConfig that you'd like to initialize at start-up and later access it in several handlers. The following example does just this:

use rocket::State;

// In a real application, this would likely be more complex.
struct MyConfig {
    user_val: String
}

#[get("/")]
fn index(state: State<MyConfig>) -> String {
    format!("The config value is: {}", state.user_val)
}

#[get("/raw")]
fn raw_config_value<'r>(state: State<'r, MyConfig>) -> &'r str {
    // use `inner()` to get a lifetime longer than `deref` gives us
    state.inner().user_val.as_str()
}

fn main() {
    let config = MyConfig {
        user_val: "user input".to_string()
    };

    rocket::ignite()
        .mount("/", routes![index, raw_config_value])
        .manage(config)
        .launch();
}

Within Request Guards

Because State is itself a request guard, managed state can be retrieved from another request guard's implementation. In the following code example, Item retrieves the MyConfig managed state in its FromRequest implementation using the Request::guard() method.

use rocket::State;
use rocket::request::{self, Request, FromRequest};

struct Item(String);

impl<'a, 'r> FromRequest<'a, 'r> for Item {
    type Error = ();

    fn from_request(request: &'a Request<'r>) -> request::Outcome<Item, ()> {
        request.guard::<State<MyConfig>>()
            .map(|my_config| Item(my_config.user_val.clone()))
    }
}

Testing with State

When unit testing your application, you may find it necessary to manually construct a type of State to pass to your functions. To do so, use the State::from() static method:

use rocket::State;

struct MyManagedState(usize);

#[get("/")]
fn handler(state: State<MyManagedState>) -> String {
    state.0.to_string()
}

let rocket = rocket::ignite().manage(MyManagedState(127));
let state = State::from(&rocket).expect("managing `MyManagedState`");
assert_eq!(handler(state), "127");

Methods

impl<'r, T: Send + Sync + 'static> State<'r, T>
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Retrieve a borrow to the underlying value with a lifetime of 'r.

Using this method is typically unnecessary as State implements Deref with a Deref::Target of T. This means Rocket will automatically coerce a State<T> to an &T as required. This method should only be used when a longer lifetime is required.

Example

use rocket::State;

struct MyConfig {
    user_val: String
}

// Use `inner()` to get a lifetime of `'r`
fn handler1<'r>(config: State<'r, MyConfig>) -> &'r str {
    &config.inner().user_val
}

// Use the `Deref` implementation which coerces implicitly
fn handler2(config: State<MyConfig>) -> String {
    config.user_val.clone()
}

Returns the managed state value in rocket for the type T if it is being managed by rocket. Otherwise, returns None.

Example

use rocket::State;

#[derive(Debug, PartialEq)]
struct Managed(usize);

#[derive(Debug, PartialEq)]
struct Unmanaged(usize);

let rocket = rocket::ignite().manage(Managed(7));

let state: Option<State<Managed>> = State::from(&rocket);
assert_eq!(state.map(|s| s.inner()), Some(&Managed(7)));

let state: Option<State<Unmanaged>> = State::from(&rocket);
assert_eq!(state, None);

Trait Implementations

impl<'a, 'r, T: Send + Sync + 'static> FromRequest<'a, 'r> for State<'r, T>
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The associated error to be returned if derivation fails.

impl<'r, T: Eq + Send + Sync + 'static> Eq for State<'r, T>
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impl<'r, T: PartialOrd + Send + Sync + 'static> PartialOrd<State<'r, T>> for State<'r, T>
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impl<'r, T: PartialEq + Send + Sync + 'static> PartialEq<State<'r, T>> for State<'r, T>
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impl<'r, T: Ord + Send + Sync + 'static> Ord for State<'r, T>
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Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl<'r, T: Debug + Send + Sync + 'static> Debug for State<'r, T>
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impl<'r, T: Send + Sync + 'static> Deref for State<'r, T>
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The resulting type after dereferencing.

impl<'r, T: Hash + Send + Sync + 'static> Hash for State<'r, T>
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Feeds a slice of this type into the given [Hasher]. Read more

Auto Trait Implementations

impl<'r, T> Send for State<'r, T>

impl<'r, T> Sync for State<'r, T>

Blanket Implementations

impl<T> From for T
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impl<T, U> Into for T where
    U: From<T>, 
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impl<T, U> TryFrom for T where
    T: From<U>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> Borrow for T where
    T: ?Sized
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impl<T, U> TryInto for T where
    U: TryFrom<T>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> BorrowMut for T where
    T: ?Sized
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impl<T> Any for T where
    T: 'static + ?Sized
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impl<T> Typeable for T where
    T: Any

Get the TypeId of this object.

impl<T> IntoCollection for T
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impl<T, I> AsResult for T where
    I: Input
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impl<Q, K> Equivalent for Q where
    K: Borrow<Q> + ?Sized,
    Q: Eq + ?Sized
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