event_hub - v1.0.0

event_hub

The event_hub module provides a way to manage and notify subscribers about events. It supports stateless observers, allowing functions to be registered and invoked in parallel when an event occurs.

Examples

Simple Observer

import gleam/io
import event_hub

pub fn main() {
  use hub <- event_hub.new()

  let unsubscribe =
    event_hub.subscribe(hub, fn(value) {
      io.println("Received value: " <> value)
    })

  event_hub.notify(hub, "Hello, world!")
  unsubscribe()
  event_hub.notify(hub, "This won't be received")
}

Types

Callback

</>

Represents a callback function that gets called with a value when an event occurs.

pub type Callback(value_type) =
  fn(value_type) -> Nil

Hub

</>

Represents a hub for managing event subscriptions and notifications.

pub type Hub(value_type)

Unsubscribe

</>

Represents an unsubscribe function that can be called to remove a previously added callback.

pub type Unsubscribe =
  fn() -> Nil

Functions

new

</> 
pub fn new(in context: fn(Hub(a)) -> b) -> b

Creates a new stateless observer hub, executes the given context with the hub, and stops the hub afterward.

Parameters

  • context: A function that takes the created Hub and returns a result.

Returns

The result of executing the context function.

Example

import event_hub

pub fn example() {
  event_hub.new(fn(hub) { event_hub.notify(hub, "event") })
}

notify

</> 
pub fn notify(on hub: Hub(a), with value: a) -> Nil

Notifies all subscribers of the hub that an event has occurred with the given value. These notifications occur in parallel but notify waits for all of them to complete.

Parameters

  • hub: The Hub to notify.
  • value: The value to send to all subscribers.

Example

import event_hub

pub fn example(hub: event_hub.Hub(String)) {
  event_hub.notify(hub, "event")
}

subscribe

</> 
pub fn subscribe(
  on hub: Hub(a),
  with callback: fn(a) -> Nil,
) -> fn() -> Nil

Adds a callback to the hub and returns an unsubscribe function.

Parameters

  • hub: The Hub to add the callback to.
  • callback: The callback function to add.

Returns

An Unsubscribe function that can be called to remove the callback.

Example

import gleam/io
import event_hub

pub fn example(hub: event_hub.Hub(String)) {
  let unsubscribe =
    event_hub.subscribe(hub, fn(value) {
      io.println("Received value: " <> value)
    })

  // To unsubscribe
  unsubscribe()
}
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