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Futures in Dioxus

Dioxus provides excellent support for asynchronous programming, allowing you to run background tasks, fetch data, and handle long-running operations without blocking your UI.

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Understanding use_future

The use_future hook spawns a future that runs in the background. Unlike use_resource, it doesn’t return a value - it’s designed for side effects and background tasks.

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Basic Usage

use dioxus::prelude::*;
use std::time::Duration;

fn app() -> Element {
    let mut count = use_signal(|| 0);
    let mut running = use_signal(|| true);

    // Spawn an infinitely running background task
    use_future(move || async move {
        loop {
            if running() {
                count += 1;
            }
            tokio::time::sleep(Duration::from_millis(400)).await;
        }
    });

    rsx! {
        div {
            h1 { "Current count: {count}" }
            button { 
                onclick: move |_| running.toggle(), 
                "Start/Stop the count"
            }
            button { 
                onclick: move |_| count.set(0), 
                "Reset the count" 
            }
        }
    }
}

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Key Characteristics

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Non-Reactive

use_future is non-reactive - it runs once when the component is first rendered and continues until:
  • The future completes
  • The component is unmounted
  • You manually cancel it

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Client-Only Execution

Important: use_future does not run on the server. If you need server-side async execution, use dioxus_core::spawn_isomorphic directly.

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Early Returns Pause Futures

When a component returns early (before reaching the use_future hook), the future is automatically paused: 
fn Child() -> Element {
    let mut early_return = use_signal(|| false);

    if early_return() {
        return rsx! { 
            button { 
                onclick: move |_| early_return.toggle(), 
                "Toggle" 
            }
        };
    }

    // This future is paused when early_return is true
    use_future(move || async move {
        loop {
            tokio::time::sleep(Duration::from_millis(100)).await;
            println!("Still running");
        }
    });

    rsx! { div { "Child component" } }
}

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Controlling Future Execution

The UseFuture handle gives you control over the future’s lifecycle:

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Methods

  • restart() - Cancel the current future and spawn a new one
  • cancel() - Forcefully stop the future
  • pause() - Temporarily pause execution
  • resume() - Resume a paused future
  • finished() - Check if the future has completed
  • state() - Get the current state (Pending, Paused, Stopped, or Ready)
fn app() -> Element {
    let mut count = use_signal(|| 0);
    
    let mut future = use_future(move || async move {
        loop {
            tokio::time::sleep(Duration::from_millis(100)).await;
            count += 1;
        }
    });

    rsx! {
        div {
            h1 { "Count: {count}" }
            button { onclick: move |_| future.restart(), "Restart" }
            button { onclick: move |_| future.pause(), "Pause" }
            button { onclick: move |_| future.resume(), "Resume" }
            button { onclick: move |_| future.cancel(), "Cancel" }
        }
    }
}

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Future States

A future can be in one of four states:
  • Pending - The future is currently running
  • Paused - The future has been temporarily paused
  • Stopped - The future has been forcefully cancelled
  • Ready - The future has completed
use dioxus::hooks::UseFutureState;

match future.state()() {
    UseFutureState::Pending => { /* Running */ },
    UseFutureState::Paused => { /* Paused */ },
    UseFutureState::Stopped => { /* Cancelled */ },
    UseFutureState::Ready => { /* Completed */ },
}

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Working with Streams

You can use use_future with async streams to process data over time: 
use futures_util::{Stream, StreamExt, stream};

fn app() -> Element {
    let mut count = use_signal(|| 0);

    use_future(move || async move {
        // Create a stream (could be from a network, file, etc.)
        let mut stream = create_number_stream();

        // Process each item from the stream
        while let Some(value) = stream.next().await {
            count.set(value);
        }
    });

    rsx! {
        h1 { "Current value: {count}" }
    }
}

fn create_number_stream() -> impl Stream<Item = i32> {
    stream::iter(0..100).then(|n| async move {
        tokio::time::sleep(Duration::from_secs(1)).await;
        n
    })
}

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Async Event Handlers

You can also run async code directly in event handlers: 
rsx! {
    button {
        onclick: move |_| async move {
            tokio::time::sleep(Duration::from_millis(500)).await;
            println!("Button clicked!");
        },
        "Click me"
    }
}
Note: If the event fires multiple times, each async handler will spawn independently.

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Comparing with use_effect

use_effect is reactive and reruns when dependencies change: 
fn app() -> Element {
    let mut count = use_signal(|| 0);

    // Runs once on mount, and whenever count changes
    use_effect(move || {
        println!("Count is now: {}", count());
        
        spawn(async move {
            // Async work here
        });
    });

    rsx! { /* ... */ }
}

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When to Use use_future

Use use_future when you need to:
  • Run a long-lived background task
  • Start a task once on component mount
  • Control task execution (pause/resume/cancel)
  • Work with streams or continuous data sources
Don’t use use_future when:
  • You need to return and display data (use use_resource instead)
  • You need reactivity to signals (use use_effect instead)
  • You need server-side rendering (use use_resource or server functions)

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Best Practices

  1. Cleanup - Futures are automatically cancelled when the component unmounts
  2. Error Handling - Handle errors within your async block
  3. Signal Updates - Use signals to communicate results back to the UI
  4. Avoid Blocking - Never block the async runtime; use .await properly
  5. Resource Cleanup - Clean up resources before the future exits

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Next Steps

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