#sycamore #helpers #server #frontend


Helper functions for sycamore

1 unstable release

0.3.0 May 24, 2022


52 lines


A library for generating REST APIs for functions.

Currently supports generating get and post APIs.

When the #[get_api] or #[post_api] macro is used, a request function is generated using reqwasm if on wasm or reqwest otherwise, and a rocket route.


// Initial function
fn plus(num1: i32, num2: i32) -> i32 {
    num1 + num2

// Normal usage
let result = plus(9, 10);

// Calling the function from client side
let result = plus_request(9, 10).await;

// Mounting the route on the server
fn rocket() -> _ {
    rocket::build().mount("/", routes![plus_route])

// The same works with GET APIs, but usually POST is recommended because it is more robust and can handle Vecs
fn minus(num1: i32, num2: i32) -> i32 {
    num1 - num2

// State can also be used!
pub fn get_all_customers(pool: &ConnectionPool) -> Result<Vec<Customer>, Error> {
        .load::<Customer>(&mut pool.get().unwrap())?)
// In this example, ConnectionPool is mounted on the rocket server, and does not need to be passed in to the request function

The example above generates a lot of code in the background. To get a better understanding of what Retrofit does, lets look at what's generated in the GET request minus function.

Code Generated

// From above
fn minus(num1: i32, num2: i32) -> i32 {
    num1 - num2

// Everything below this point is generated.

// Route generated
fn minus_route(num1: String, num2: String) -> String {

// Request function generated
async fn minus_request(num1: i32, num2: i32) -> i32 {

Feature Flags

server - contains generated Rocket routes

client - contains generated request function

These features serve as a way to use the same code on a server and client. By default they are both enabled, but if you have functions with a generated API in a crate of your own, and you use client/server feature flags, you can import the same crate on both backend and frontend, and your backend code won't be packaged with frontend code. This is usefull if you are targeting WASM on the frontend and using a DB system like Diesel (not supported on WASM) for your backend.


  • Basic get_api
  • Add server and client feature support (allows the exclusion of the route/request functions)
  • Support async functions
  • Add post_api
  • Support references
  • Support generics
  • Support other HTTP client libraries (surf, etc.)
  • Support other HTTP server libraries (warp, actix, etc.)
  • Support Rocket States
  • Better ergonomics for Rocket States (no attributes passed in, state not required to be last arg)


~192K SLoC