Hot reloading while in development for Gleam!

Radiate will watch any directory you specify for changes. When a file is changed in that directory, it'll check if it's a Gleam file, and if it is, the project will be recompiled and all modified modules will be reloaded, without having to restart the BEAM VM.

// On main.gleam
import gleam/erlang/process
import gleam/io
import radiate
import message

pub fn main() {
  let _ =
    radiate.new()
    |> radiate.add_dir("src")
    |> radiate.start()

  let timer_subject = process.new_subject()

  print_every_second(timer_subject)
}

fn print_every_second(subject: process.Subject(Nil)) {
  process.send_after(subject, 1000, Nil)

  let _ = process.receive(subject, 1500)
  io.println(message.get_message())

  print_every_second(subject)
}

// On message.gleam
pub fn get_message() -> String {
  "Hello!"
}

When you first run this, it'll print "Hello!" every second.

Now, go ahead and change the text get_message returns to "Hello, world!", and save the file.

As soon as you save, the message printed is changed to "Hello, world!", without needing to restart the program!

Right now, the add_dir function only supports "." or an absolute path! Be careful to resolve the path to get it work if you want to watch "src" for example.

You can add callbacks to be run every time code is reloaded through on_reload:

import radiate
import gleam/io

pub fn main() {
  let _ = radiate.new()
    |> radiate.add_dir("src")
    |> radiate.on_reload(fn (_state, path) {
      io.println("Change in " <> path <> ", reloading!")
    })
    |> radiate.start()
}

This package can be added to your Gleam project:

gleam add radiate

and its documentation can be found at https://hexdocs.pm/radiate.