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Pockets is an Elixir wrapper around Erlang ETS and DETS, Erlang's built-in solutions for memory- and disk-based term storage. Pockets aims to provide a simple and familiar interface for caching and persisting data by implementing many of the functions found in the built-in Map and Keyword modules. A pocket may hold data in memory or on disk.

For those needing more power or versatility than what :ets or :dets can offer, Elixir includes :mnesia.

Secondly, the docs on erlang.org are a bit rough to look at for Elixir developers, so this package acts as a case study of the differences between the powerful built-in :ets and :dets libraries.

In case it was too subtle, "Pockets" is a name that includes "ETS" for mnemonic purposes.


Add pockets to your list of dependencies in mix.exs:

def deps do
    {:pockets, "~> 0.1.0"}


A simple memory-based cache requires no special arguments:

iex> Pockets.new(:my_cache)
{:ok, :my_cache}
iex> Pockets.put(:my_cache, :a, "Apple") |> Pockets.put(:b, "boy") |> Pockets.put(:c, "Charlie")
iex> Pockets.get(:my_cache, :c)

Using a disk-based cache is appropriate when you need your data to persist. Just supply a file path as the second argument to Pockets.new/3:

iex> Pockets.new(:on_disk, "/tmp/cache.dets")
{:ok, :on_disk}

You can easily populate your pocket with existing data:

iex> Pockets.new(:on_disk, "/tmp/cache.dets")
{:ok, :on_disk}
iex> Pockets.merge(:on_disk, %{x: "xylophone", y: "yellow"})

You can easily inspect your data, e.g. using Pockets.to_map/1:

iex> Pockets.to_map(:on_disk)
%{x: "xylophone", y: "yellow"}

See the Pockets module documentation for more info!

Image Attribution

"pocket" by Hilmi Hidayat from the Noun Project