# `Trogon.Commanded.CommandHandler`
[🔗](https://github.com/straw-hat-team/beam-monorepo/blob/trogon_commanded@v1.0.1/apps/trogon_commanded/lib/trogon/commanded/command_handler.ex#L1)

Defines a module as a "Command Handler". For more information about commands, please read the following:

- [CQRS pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/cqrs)

# `__using__`
*macro* 

```elixir
@spec __using__(opts :: []) :: any()
```

Convert the module into a `Commanded.Commands.Handler`.

Use `Commanded.Aggregate.Multi` to generate multiple events from
a single command. This can be useful when you want to emit multiple events
that depend upon the aggregate state being updated.

## Usage

    defmodule MyCommandHandler do
      use Trogon.Commanded.CommandHandler

      @impl Commanded.Commands.Handler
      def handle(account, command) do
        account
        |> Multi.new()
        |> Multi.execute(&withdraw_money(&1, command.amount))
        |> Multi.execute(&check_balance/1)
      end

      defp withdraw_money(account, amount) do
        # ...
      end

      defp check_balance(account, amount) do
        # ...
      end
    end

---

*Consult [api-reference.md](api-reference.md) for complete listing*