GenEvent
GenEvent[edit]
GenEvent is a behavior module in the Elixir programming language that allows for event-driven programming. With GenEvent, users can implement generic event handling modules that can be subscribed to by multiple processes.
Usage[edit]
To define and use a GenEvent module, the following steps can be followed:
1. First, define the behavior by using the `defmodule` directive with the `@behaviour` attribute:
```elixir defmodule MyEventModule do
@behaviour GenEvent ...
end ```
2. Implement the callback functions required by the GenEvent behavior:
```elixir def handle_event(state, event, acc) do
# handle the event
...
{:ok, new_state}
end
def handle_call(state, event, acc) do
# handle synchronous call
...
{:reply, reply, new_state}
end ```
3. Create a GenEvent process by calling `GenEvent.start_link(module, args)`:
```elixir {:ok, pid} = GenEvent.start_link(MyEventModule, initial_state) ```
4. Subscribe interested processes to the GenEvent by using `GenEvent.add_handler`:
```elixir GenEvent.add_handler(pid, handler) ```
5. Trigger an event by invoking `GenEvent.notify`:
```elixir GenEvent.notify(pid, event) ```
Example[edit]
Here is an example that illustrates the usage of GenEvent:
```elixir defmodule MyEventModule do
@behaviour GenEvent
def handle_event(state, event, acc) do
IO.puts("Handling event: #{event}")
{:ok, state}
end
def handle_call(state, event, acc) do
IO.puts("Handling synchronous call: #{event}")
{:reply, event * 2, state}
end
end
{:ok, pid} = GenEvent.start_link(MyEventModule, {}) GenEvent.add_handler(pid, self())
GenEvent.notify(pid, :my_event) reply = GenEvent.call(pid, :my_synchronous_event)
IO.puts("Received reply from event: #{reply}") ```