cargo add leptos_query --optional

[features]
hydrate = [
    "leptos_query/hydrate",
    # ...
]
ssr = [
    "leptos_query/ssr",
    # ...
 ]

use leptos_query::*;
use leptos::*;

#[component]
pub fn App(cx: Scope) -> impl IntoView {
    // Provides Query Client for entire app.
    provide_query_client(cx);

    // Rest of App...
}

 use leptos::*;
 use leptos_query::*;
 use std::time::Duration;
 use serde::*;

 // Data type.
 #[derive(Clone, Deserialize, Serialize)]
 struct Monkey {
     name: String,
 }

 // Create a Newtype for MonkeyId.
 #[derive(Clone, PartialEq, Eq, Hash)]
 struct MonkeyId(String);


 // Monkey fetcher.
 async fn get_monkey(id: MonkeyId) -> Monkey {
    todo!()
 }

 // Query for a Monkey.
 fn use_monkey_query(cx: Scope, id: impl Fn() -> MonkeyId + 'static) -> QueryResult<Monkey> {
     leptos_query::use_query(
         cx,
         id,
         get_monkey,
         QueryOptions {
             default_value: None,
             refetch_interval: None,
             resource_option: ResourceOption::NonBlocking,
             // Considered stale after 5 seconds.
             stale_time: Some(Duration::from_secs(5)),
             // Infinite cache time.
             cache_time: None,
         },
     )
 }

#[component]
fn MonkeyView(cx: Scope, id: MonkeyId) -> impl IntoView {
    let query = use_monkey_query(cx, move || id.clone());
    let QueryResult {
        data,
        is_loading,
        is_fetching,
        is_stale
        ..
    } = query;

    view! { cx,
      // You can use the query result data here.
      // Everything is reactive.
       

           

               "Loading Status: "
               {move || { if is_loading.get() { "Loading..." } else { "Loaded" } }}
           
           

               "Fetching Status: "
               
                   {move || { if is_fetching.get() { "Fetching..." } else { "Idle" } }}
               
           
           

               "Stale Status: "
               
                   {move || { if is_stale.get() { "Stale" } else { "Fresh" } }}
               
           
           // Query data should be read inside a Transition/Suspense component.
           <Transition
               fallback=move || {
                   view! { cx, 
"Loading..."
 }
               }>
               {move || {
                   data.get()
                       .map(|monkey| {
                           view! { cx, 
{monkey.name}
 }
                       })
               }}
           Transition>
       
    }
}

For a complete working example see the example directory

FAQ

How's this different from a leptos Resource?

A Query uses a resource under the hood, but provides additional functionality like caching, de-duplication, and invalidation.

Resources are individually bound to the Scope they are created in. Queries are all bound to the QueryClient they are created in. Meaning, once you have a QueryClient in your app, you can access the value for a query anywhere in your app.

With a resource, you have to manually lift it to a higher scope if you want to preserve it. And this can be cumbersome if you have a many resources.

Also, queries are stateful on a per-key basis, meaning you can use the same query with for the same key in multiple places and only one request will be made, and they all share the same state.

What's the difference between stale_time and cache_time?

staleTime is the duration until a query transitions from fresh to stale. As long as the query is fresh, data will always be read from the cache only.

When a query is stale, it will be refetched on its next usage.

cacheTime is the duration until inactive queries will be removed from cache.

• Default value for stale_time is 0 seconds.
• Default value for cache_time is 5 minutes.

These can be configured per-query using QueryOptions

If you want infinite cache/stale time, you can set stale_time and cache_time to None.

NOTE: stale_time can never be greater than cache_time. If stale_time is greater than cache_time, stale_time will be set to cache_time.

What's a QueryClient?

A QueryClient allows you to interact with the query cache. You can invalidate queries, prefetch them, and introspect the query cache.

use_query_client() will return the QueryClient for the current scope.

What's invalidating a query do?

Sometimes you can't wait for a query to become stale before you refetch it. QueryClient has an invalidate_query method that lets you intelligently mark queries as stale and potentially refetch them too!

When a query is invalidated, the following happens:

• It is marked as invalid. This invalid state overrides any stale_time configuration.
• The next time the query is used, it will be refetched in the background.
  • If a query is currently being used, it will be refetched immediately.

What's the difference between is_loading and is_fetching?

is_fetching is true when the query is in the process of fetching data.

is_loading is true when the query is in the process of fetching data FOR THE FIRST TIME.