Struct rocket::State[][src]

#[repr(transparent)]
pub struct State<T: Send + Sync + 'static>(_);
Expand description

Request guard to retrieve managed state.

A reference &State<T> type is a request guard which retrieves the managed state managing for some type T. 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 as multiple handlers in multiple threads may be accessing the value at once. 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(state: &State<MyConfig>) -> &str {
    &state.user_val
}

#[launch]
fn rocket() -> _ {
    rocket::build()
        .mount("/", routes![index, raw_config_value])
        .manage(MyConfig { user_val: "user input".to_string() })
}

Within Request Guards

Because State is itself a request guard, managed state can be retrieved from another request guard’s implementation using either Request::guard() or Rocket::state(). In the following code example, the Item request guard retrieves MyConfig from managed state:

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

struct Item<'r>(&'r str);

#[rocket::async_trait]
impl<'r> FromRequest<'r> for Item<'r> {
    type Error = ();

    async fn from_request(request: &'r Request<'_>) -> request::Outcome<Self, ()> {
        // Using `State` as a request guard. Use `inner()` to get an `'r`.
        let outcome = request.guard::<&State<MyConfig>>().await
            .map(|my_config| Item(&my_config.user_val));

        // Or alternatively, using `Rocket::state()`:
        let outcome = request.rocket().state::<MyConfig>()
            .map(|my_config| Item(&my_config.user_val))
            .or_forward(());

        outcome
    }
}

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::get() static method or the From<&T> implementation:

use rocket::State;

struct MyManagedState(usize);

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

let mut rocket = rocket::build().manage(MyManagedState(127));
let state = State::get(&rocket).expect("managed `MyManagedState`");
assert_eq!(handler(state), "127");

let managed = MyManagedState(77);
assert_eq!(handler(State::from(&managed)), "77");

Implementations

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::build().manage(Managed(7));

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

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

Borrow the inner value.

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;

#[derive(Clone)]
struct MyConfig {
    user_val: String
}

fn handler1<'r>(config: &State<MyConfig>) -> String {
    let config = config.inner().clone();
    config.user_val
}

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

Trait Implementations

Formats the value using the given formatter. Read more

The resulting type after dereferencing.

Dereferences the value.

Formats the value using the given formatter. Read more

Performs the conversion.

The associated error to be returned if derivation fails.

Derives an instance of Self from the incoming request metadata. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

This method returns an ordering between self and other values if one exists. Read more

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Returns true if launch should be aborted and false otherwise.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Converts self into T using Into<T>. Read more

Converts self into a target type. Read more

Compare self to key and return true if they are equal.

Causes self to use its Binary implementation when Debug-formatted.

Causes self to use its Display implementation when Debug-formatted. Read more

Causes self to use its LowerExp implementation when Debug-formatted. Read more

Causes self to use its LowerHex implementation when Debug-formatted. Read more

Causes self to use its Octal implementation when Debug-formatted.

Causes self to use its Pointer implementation when Debug-formatted. Read more

Causes self to use its UpperExp implementation when Debug-formatted. Read more

Causes self to use its UpperHex implementation when Debug-formatted. Read more

Performs the conversion.

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

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

Performs the conversion.

Converts self into a collection.

Pipes by value. This is generally the method you want to use. Read more

Borrows self and passes that borrow into the pipe function. Read more

Mutably borrows self and passes that borrow into the pipe function. Read more

Borrows self, then passes self.borrow() into the pipe function. Read more

Mutably borrows self, then passes self.borrow_mut() into the pipe function. Read more

Borrows self, then passes self.as_ref() into the pipe function.

Mutably borrows self, then passes self.as_mut() into the pipe function. Read more

Borrows self, then passes self.deref() into the pipe function.

Mutably borrows self, then passes self.deref_mut() into the pipe function. Read more

Pipes a value into a function that cannot ordinarily be called in suffix position. Read more

Pipes a trait borrow into a function that cannot normally be called in suffix position. Read more

Pipes a trait mutable borrow into a function that cannot normally be called in suffix position. Read more

Pipes a trait borrow into a function that cannot normally be called in suffix position. Read more

Pipes a trait mutable borrow into a function that cannot normally be called in suffix position. Read more

Pipes a dereference into a function that cannot normally be called in suffix position. Read more

Pipes a mutable dereference into a function that cannot normally be called in suffix position. Read more

Pipes a reference into a function that cannot ordinarily be called in suffix position. Read more

Pipes a mutable reference into a function that cannot ordinarily be called in suffix position. Read more

Should always be Self

Immutable access to a value. Read more

Mutable access to a value. Read more

Immutable access to the Borrow<B> of a value. Read more

Mutable access to the BorrowMut<B> of a value. Read more

Immutable access to the AsRef<R> view of a value. Read more

Mutable access to the AsMut<R> view of a value. Read more

Immutable access to the Deref::Target of a value. Read more

Mutable access to the Deref::Target of a value. Read more

Calls .tap() only in debug builds, and is erased in release builds.

Calls .tap_mut() only in debug builds, and is erased in release builds. Read more

Calls .tap_borrow() only in debug builds, and is erased in release builds. Read more

Calls .tap_borrow_mut() only in debug builds, and is erased in release builds. Read more

Calls .tap_ref() only in debug builds, and is erased in release builds. Read more

Calls .tap_ref_mut() only in debug builds, and is erased in release builds. Read more

Calls .tap_deref() only in debug builds, and is erased in release builds. Read more

Calls .tap_deref_mut() only in debug builds, and is erased in release builds. Read more

Provides immutable access for inspection. Read more

Calls tap in debug builds, and does nothing in release builds.

Provides mutable access for modification. Read more

Calls tap_mut in debug builds, and does nothing in release builds.

Provides immutable access to the reference for inspection.

Calls tap_ref in debug builds, and does nothing in release builds.

Provides mutable access to the reference for modification.

Calls tap_ref_mut in debug builds, and does nothing in release builds.

Provides immutable access to the borrow for inspection. Read more

Calls tap_borrow in debug builds, and does nothing in release builds.

Provides mutable access to the borrow for modification.

Calls tap_borrow_mut in debug builds, and does nothing in release builds. Read more

Immutably dereferences self for inspection.

Calls tap_deref in debug builds, and does nothing in release builds.

Mutably dereferences self for modification.

Calls tap_deref_mut in debug builds, and does nothing in release builds. Read more

Converts the given value to a String. Read more

Attempts to convert self into T using TryInto<T>. Read more

Attempts to convert self into a target type. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.