Elixir 1.4
Elixir 1.4
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Agent

Agent

Agents are a simple abstraction around state.

Often in Elixir there is a need to share or store state that must be accessed from different processes or by the same process at different points in time.

The Agent module provides a basic server implementation that allows state to be retrieved and updated via a simple API.

Examples

For example, in the Mix tool that ships with Elixir, we need to keep a set of all tasks executed by a given project. Since this set is shared, we can implement it with an Agent:

defmodule Mix.TasksServer do
  def start_link do
    Agent.start_link(fn -> MapSet.new end, name: __MODULE__)
  end

  @doc "Checks if the task has already executed"
  def executed?(task, project) do
    item = {task, project}
    Agent.get(__MODULE__, fn set ->
      item in set
    end)
  end

  @doc "Marks a task