Registry.values

You're seeing just the function values, go back to Registry module for more information.
Link to this function

values(registry, key, pid)

View Source (since 1.12.0)

Specs

values(registry(), key(), pid()) :: [value()]

Reads the values for the given key for pid in registry.

For unique registries, it is either an empty list or a list with a single element. For duplicate registries, it is a list with zero, one, or multiple elements.

Examples

In the example below we register the current process and look it up both from itself and other processes:

iex> Registry.start_link(keys: :unique, name: Registry.UniqueLookupTest)
iex> Registry.values(Registry.UniqueLookupTest, "hello", self())
[]
iex> {:ok, _} = Registry.register(Registry.UniqueLookupTest, "hello", :world)
iex> Registry.values(Registry.UniqueLookupTest, "hello", self())
[:world]
iex> Task.async(fn -> Registry.values(Registry.UniqueLookupTest, "hello", self()) end) |> Task.await()
[]
iex> parent = self()
iex> Task.async(fn -> Registry.values(Registry.UniqueLookupTest, "hello", parent) end) |> Task.await()
[:world]

The same applies to duplicate registries:

iex> Registry.start_link(keys: :duplicate, name: Registry.DuplicateLookupTest)
iex> Registry.values(Registry.DuplicateLookupTest, "hello", self())
[]
iex> {:ok, _} = Registry.register(Registry.DuplicateLookupTest, "hello", :world)
iex> Registry.values(Registry.DuplicateLookupTest, "hello", self())
[:world]
iex> {:ok, _} = Registry.register(Registry.DuplicateLookupTest, "hello", :another)
iex> Enum.sort(Registry.values(Registry.DuplicateLookupTest, "hello", self()))
[:another, :world]