Struct leptos::Resource

pub struct Resource<S, T>where
    S: 'static,
    T: 'static,{ /* private fields */ }

A signal that reflects the current state of an asynchronous task, allowing you to integrate async Futures into the synchronous reactive system.

Takes a fetcher function that generates a Future when called and a source signal that provides the argument for the fetcher. Whenever the value of the source changes, a new Future will be created and run.

When server-side rendering is used, the server will handle running the Future and will stream the result to the client. This process requires the output type of the Future to be Serializable. If your output cannot be serialized, or you just want to make sure the Future runs locally, use create_local_resource().

// any old async function; maybe this is calling a REST API or something
async fn fetch_cat_picture_urls(how_many: i32) -> Vec<String> {
  // pretend we're fetching cat pics
  vec![how_many.to_string()]
}

// a signal that controls how many cat pics we want
let (how_many_cats, set_how_many_cats) = create_signal(cx, 1);

// create a resource that will refetch whenever `how_many_cats` changes
let cats = create_resource(cx, how_many_cats, fetch_cat_picture_urls);

// when we read the signal, it contains either
// 1) None (if the Future isn't ready yet) or
// 2) Some(T) (if the future's already resolved)
assert_eq!(cats(), Some(vec!["1".to_string()]));

// when the signal's value changes, the `Resource` will generate and run a new `Future`
set_how_many_cats(2);
assert_eq!(cats(), Some(vec!["2".to_string()]));

Implementations

impl<S, T> Resource<S, T>where
    S: Clone + 'static,
    T: 'static,

pub fn read(&self) -> Option<T>where
    T: Clone,

Clones and returns the current value of the resource (Option::None if the resource is still pending). Also subscribes the running effect to this resource.

If you want to get the value without cloning it, use Resource::with. (value.read() is equivalent to value.with(T::clone).)

pub fn with<U>(&self, f: impl FnOnce(&T) -> U) -> Option<U>

Applies a function to the current value of the resource, and subscribes the running effect to this resource. If the resource hasn’t yet resolved, the function won’t be called and this will return Option::None.

If you want to get the value by cloning it, you can use Resource::read.

pub fn loading(&self) -> ReadSignal<bool>

Returns a signal that indicates whether the resource is currently loading.

pub fn refetch(&self)

Re-runs the async function with the current source data.

Trait Implementations

impl<S, T> Clone for Resource<S, T>where
    S: Clone + 'static,
    T: Clone + 'static,

fn clone(&self) -> Resource<S, T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<S, T> Debug for Resource<S, T>where
    S: Debug + 'static,
    T: Debug + 'static,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<S, T> Fn() for Resource<S, T>where
    S: Clone + 'static,
    T: Clone + 'static,

extern "rust-call" fn call(
    &self,
    _args: ()
) -> <Resource<S, T> as FnOnce()>::Output

🔬This is a nightly-only experimental API. (fn_traits)

Performs the call operation.

impl<S, T> FnMut() for Resource<S, T>where
    S: Clone + 'static,
    T: Clone + 'static,

extern "rust-call" fn call_mut(
    &mut self,
    _args: ()
) -> <Resource<S, T> as FnOnce()>::Output

🔬This is a nightly-only experimental API. (fn_traits)

Performs the call operation.

impl<S, T> FnOnce() for Resource<S, T>where
    S: Clone + 'static,
    T: Clone + 'static,

type Output = Option<T>

The returned type after the call operator is used.

extern "rust-call" fn call_once(
    self,
    _args: ()
) -> <Resource<S, T> as FnOnce()>::Output

🔬This is a nightly-only experimental API. (fn_traits)

Performs the call operation.

impl<S, T> Hash for Resource<S, T>where
    S: Hash + 'static,
    T: Hash + 'static,

fn hash<__H>(&self, state: &mut __H)where
    __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)where
    H: Hasher,
    Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<S, T> PartialEq<Resource<S, T>> for Resource<S, T>where
    S: PartialEq<S> + 'static,
    T: PartialEq<T> + 'static,

fn eq(&self, other: &Resource<S, T>) -> bool

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

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<S, T> Copy for Resource<S, T>where
    S: Clone + 'static,
    T: Clone + 'static,

impl<S, T> Eq for Resource<S, T>where
    S: Eq + 'static,
    T: Eq + 'static,

impl<S, T> StructuralEq for Resource<S, T>where
    S: 'static,
    T: 'static,

impl<S, T> StructuralPartialEq for Resource<S, T>where
    S: 'static,
    T: 'static,