Struct rocket::State
[−]
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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 the
manage method. 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())) } }
Methods
impl<'r, T: Send + Sync + 'static> State<'r, T>
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fn inner(&self) -> &'r T
Retrieve a borrow to the underyling value with a lifetime of 'r
.
Using this method is typically unnecessary as State
implements Deref
with a 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() }
Trait Implementations
impl<'r, T: Debug + Send + Sync + 'static> Debug for State<'r, T>
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impl<'r, T: PartialEq + Send + Sync + 'static> PartialEq for State<'r, T>
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fn eq(&self, __arg_0: &State<'r, T>) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, __arg_0: &State<'r, T>) -> bool
This method tests for !=
.
impl<'r, T: Eq + Send + Sync + 'static> Eq for State<'r, T>
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impl<'r, T: PartialOrd + Send + Sync + 'static> PartialOrd for State<'r, T>
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fn partial_cmp(&self, __arg_0: &State<'r, T>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, __arg_0: &State<'r, T>) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, __arg_0: &State<'r, T>) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
fn gt(&self, __arg_0: &State<'r, T>) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, __arg_0: &State<'r, T>) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl<'r, T: Ord + Send + Sync + 'static> Ord for State<'r, T>
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fn cmp(&self, __arg_0: &State<'r, T>) -> Ordering
This method returns an Ordering
between self
and other
. Read more
fn max(self, other: Self) -> Self
ord_max_min
)Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
ord_max_min
)Compares and returns the minimum of two values. Read more
impl<'r, T: Hash + Send + Sync + 'static> Hash for State<'r, T>
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fn hash<__HT: Hasher>(&self, __arg_0: &mut __HT)
Feeds this value into the given [Hasher
]. Read more
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
1.3.0
H: Hasher,
Feeds a slice of this type into the given [Hasher
]. Read more
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>, ()>
Derives an instance of Self
from the incoming request metadata. Read more