Struct rocket::State [−][src]
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
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
Auto Trait Implementations
impl<T> RefUnwindSafe for State<T> where
T: RefUnwindSafe,
impl<T> UnwindSafe for State<T> where
T: UnwindSafe,