aharpole

defmodule IncrementableValue do
  use StateMapGenServer

  def start_link(config \\ []) do
    config = Keyword.merge([increment_by: 1], config)
    GenServer.start_link(__MODULE__, config, [])
  end

  def init(config) do
    {:ok, %{value: 1}, config}

aharpole

GenServer.update_config(pid, fn config -> Keyword.update(config, :increment_by, 2) end)

aharpole

def handle_cast(:increment, %{value: value, increment_by: increment_by}) do
  {:ok, %{value: value + increment_by}}
end

aharpole

defmodule IncrementableValue do
  use GenServer

  defstruct [:value, :increment_by]

  @type t :: %__MODULE__{
    value: integer,
    increment_by: integer
  }

aharpole

def handle_cast(:increment, state) do
  new_state = Map.put(state, :value, &(&1 + state.increment_by))
  {:noreply, state}
end

aharpole

def handle_call(:get_data, _, %{value: value} = state) do
  {:reply, value, state}
end

aharpole

def init(%{increment_by: increment_by}) do
  {:ok, %__MODULE__{value: 1, increment_by: increment_by}}
end

aharpole

def start_link(opts) do
  {state_opts, opts} = Keyword.split(opts, [:increment_by])
  state_opts = Keyword.merge([increment_by: 1], state_opts) #default to incrementing by 1 still
  GenServer.start_link(__MODULE__, state_opts, opts)
end

aharpole

@type t :: %__MODULE__{
  value: integer,
  increment_by: integer
}

aharpole

defstruct [:value, :increment_by]