#  Envío [](https://kantox.com/)  
**Application-wide registry with handy helpers to ease dispatching.**
## Installation
Simply add `envio` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:envio, "~> 0.3"}
]
end
```
## Usage
### Simple publisher
Use `Envio.Publisher` helper to scaffold the registry publisher. It provides
`broadcast/2` helper (and `brodcast/1` if the default channel is set.)
```elixir
defmodule Spitter.Registry do
use Envio.Publisher, channel: :main
def spit(channel, what), do: broadcast(channel, what)
def spit(what), do: broadcast(what)
end
```
### Simple subscriber ([`dispatch`](https://hexdocs.pm/elixir/master/Registry.html#module-using-as-a-dispatcher))
Just register your handler anywhere in the code:
```elixir
Envio.register(
{Sucker, :suck},
dispatch: %Envio.Channel{source: Spitter.Registry, name: :foo}
)
```
`Sucker.suck/1` will be called with a payload.
### PubSub subscriber ([`pub_sub`](https://hexdocs.pm/elixir/master/Registry.html#module-using-as-a-pubsub))
Use `Envio.Subscriber` helper to scaffold the registry subscriber. Implement
`handle_envio/2` for custom message handling. The default implementation
collects last 10 messages in it’s state.
```elixir
defmodule PubSucker do
use Envio.Subscriber, channels: [{Spitter.Registry, :foo}]
def handle_envio(message, state) do
{:noreply, state} = super(message, state)
IO.inspect({message, state}, label: "PubSucked")
{:noreply, state}
end
end
```
### Phoenix.PubSub subscriber ([`phoenix_pub_sub`](https://hexdocs.pm/phoenix_pubsub))
Use `manager: :phoenix_pub_sub` for distributed message broadcasting. The implementation below subscribes to `"main"` channel in the distributed OTP environment and prints out each subsequent incoming message to standard output.
```elixir
defmodule Pg2Sucker do
use Envio.Subscriber, channels: ["main"], manager: :phoenix_pub_sub
def handle_envio(message, state) do
{:noreply, state} = super(message, state)
IO.inspect({message, state}, label: "Received")
{:noreply, state}
end
end
```
The publisher this subscriber might be listening to would look like
```elixir
defmodule Pg2Spitter do
use Envio.Publisher, manager: :phoenix_pub_sub, channel: "main"
def spit(channel, what), do: broadcast(channel, what)
def spit(what), do: broadcast(what)
end
```
## Changelog
- **`0.10.1`** → Runtime configs for backends via `{:system, value}` tuples
- **`0.10.0`** → `Process` backend
- **`0.8.0`** → `Phoenix.PubSub` support (+ backend)
- **`0.5.0`** → removed a dependency from `Slack` package
- **`0.4.0`** → better docs and other enhancements
- **`0.3.0`** → `Envio.Backend` and infrastructure for backends; `Slack` as an example.
## ToDo
- Back pressure with [`GenStage`](https://hexdocs.pm/gen_stage/GenStage.html)
for `:dispatch` kind of delivery;
- Set of backends for easy delivery (_slack_, _redis_, _rabbit_, etc.)
## [Documentation](https://hexdocs.pm/envio)
