feat: async higher order fn

Cargo.toml

@@ -10,6 +10,7 @@ path = "src/lib.rs"
 doctest = false
 
 [dependencies]
+tokio = { version = "1.40", default-features= false, features = ["macros", "rt-multi-thread" ] }
 unicode-segmentation = "1"
 
 [profile.release]

README.md

@@ -1,9 +1,10 @@
 # Rust gems
 
-This repository offers some Rust snippets that might be useful when studying the language.
+This repository offers some Rust snippets that can be useful when studying the language.
 
 - [vec_any](src/vec_any.rs) Collect trait objects in a vector and use downcast_ref to access the concrete type instances of the items
-- [mutate_in_closure](src/mutate_in_closure.rs) Mutate a value in a closure without copy and clone
+- [mutate_in_closure](src/mutate_in_closure.rs) Mutate a value in a closure without copy and clone by using Rc
+- [async_higher_order_fn](src/async_higher_order_fn.rs) Implement an async higher order function that accept an async closures and returns an async result
 - [from_str](src/from_str.rs) Thou shall not implement From\<str'> but instead implement the FromStr trait
 - [graphemes](src/graphemes.rs) Trim an unicode string to a maximum length with
 

src/async_higher_order_fn.rs

@@ -0,0 +1,46 @@
+#![allow(dead_code, unused)]
+
+use std::{error::Error, future::Future, pin::Pin};
+
+/// function that accepts an async function handler
+fn higher_order_function(f: FunctionHandler, data: Data) -> Pin<Box<dyn Future<Output = Response>>> {
+  f(data)
+}
+
+pub type FunctionHandler = &'static (dyn Fn(Data) -> Pin<Box<dyn Future<Output = Response>>>);
+pub type Response = Result<ResponseData, Box<dyn Error>>;
+
+fn my_function_handler(data: Data) -> Pin<Box<dyn Future<Output = Response>>> {
+  Box::pin(async move { async_dummy().await })
+}
+
+/// Dummy async function to demonstrate calling a async function from a async higher order function
+async fn async_dummy() -> Result<ResponseData, Box<dyn Error>> {
+  Ok(ResponseData { processed: true })
+}
+
+pub struct Data {
+  title: String,
+}
+
+pub struct ResponseData {
+  processed: bool,
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[tokio::test]
+  async fn test_call_it() {
+    let response = higher_order_function(
+      &my_function_handler,
+      Data {
+        title: "Hello".to_string(),
+      },
+    )
+    .await;
+    assert!(response.is_ok());
+    assert!(response.unwrap().processed);
+  }
+}

src/lib.rs

@@ -1,3 +1,4 @@
+mod async_higher_order_fn;
 pub mod from_str;
 pub mod graphemes;
 pub mod mutate_in_closure;