Future Functions

Async utility functions

std::future::ready

use std::future::Future;

async fn use_ready() -> i32 {
    // ready() creates immediately-ready future
    let future = std::future::ready(42);
    future.await
}

fn main() {
    // ready creates a future that's already complete
    let future = std::future::ready("hello");

    println!("=== std::future::ready ===");
    println!("Creates Future that immediately returns value");
    println!();

    // Use case: returning from async fn without await
    async fn get_cached(use_cache: bool) -> String {
        if use_cache {
            std::future::ready("cached".to_string()).await
        } else {
            // actual async work
            "fetched".to_string()
        }
    }

    // Type signature
    fn returns_future() -> impl Future<Output = i32> {
        std::future::ready(42)
    }

    println!("Common uses:");
    println!("- Return early from async fn");
    println!("- Mock async operations");
    println!("- Convert sync to async API");
}