[−][src]Struct rocket::State
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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pub fn inner(&self) -> &'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() }
pub fn from(rocket: &'r Rocket) -> Option<Self>
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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<'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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impl<'r, T: Eq + Send + Sync + 'static> Eq for State<'r, T>
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impl<'a, 'r, T: Send + Sync + 'static> FromRequest<'a, 'r> for State<'r, T>
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type Error = ()
The associated error to be returned if derivation fails.
fn from_request(req: &'a Request<'r>) -> Outcome<State<'r, T>, ()>
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impl<'r, T: Hash + Send + Sync + 'static> Hash for State<'r, T>
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fn hash<__H: Hasher>(&self, state: &mut __H)
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fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
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H: Hasher,
impl<'r, T: Ord + Send + Sync + 'static> Ord for State<'r, T>
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fn cmp(&self, other: &State<'r, T>) -> Ordering
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#[must_use]fn max(self, other: Self) -> Self
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#[must_use]fn min(self, other: Self) -> Self
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#[must_use]fn clamp(self, min: Self, max: Self) -> Self
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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: PartialOrd + Send + Sync + 'static> PartialOrd<State<'r, T>> for State<'r, T>
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fn partial_cmp(&self, other: &State<'r, T>) -> Option<Ordering>
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fn lt(&self, other: &State<'r, T>) -> bool
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fn le(&self, other: &State<'r, T>) -> bool
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fn gt(&self, other: &State<'r, T>) -> bool
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fn ge(&self, other: &State<'r, T>) -> bool
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impl<'r, T: Send + Sync + 'static> StructuralEq for State<'r, T>
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impl<'r, T: Send + Sync + 'static> StructuralPartialEq for State<'r, T>
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Auto Trait Implementations
impl<'r, T> RefUnwindSafe for State<'r, T> where
T: RefUnwindSafe,
T: RefUnwindSafe,
impl<'r, T> Send for State<'r, T>
impl<'r, T> Sync for State<'r, T>
impl<'r, T> Unpin for State<'r, T>
impl<'r, T> UnwindSafe for State<'r, T> where
T: RefUnwindSafe,
T: RefUnwindSafe,
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T, I> AsResult<T, I> for T where
I: Input,
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I: Input,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<Q, K> Equivalent<K> for Q where
K: Borrow<Q> + ?Sized,
Q: Eq + ?Sized,
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K: Borrow<Q> + ?Sized,
Q: Eq + ?Sized,
fn equivalent(&self, key: &K) -> bool
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> IntoCollection<T> for T
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fn into_collection<A>(self) -> SmallVec<A> where
A: Array<Item = T>,
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A: Array<Item = T>,
fn mapped<U, F, A>(self, f: F) -> SmallVec<A> where
A: Array<Item = U>,
F: FnMut(T) -> U,
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A: Array<Item = U>,
F: FnMut(T) -> U,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Typeable for T where
T: Any,
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T: Any,