Returns a specification to start this module under a supervisor.

See Supervisor.

@spec start_link(any()) :: Supervisor.on_start()

Starts a supervisor with dynamic supervisor and process registry.

@spec via_registry(term()) :: {:via, Registry, term()}

Returns a :via name to be used in the helper process registry.

@spec with_helper(any(), child_spec, (pid() -> any())) :: any()
when child_spec: :supervisor.child_spec() | {module(), term()} | module()

Executes a given callback over running helper.

Checks whether the helper with name registered under helper registry is already running. If not, then it starts the process according to child_spec under the dynamic supervisor. In either case, it passes the helper process pid to the callback.

It is the responsibility of the helper process to register its name with the helper registry via the via_registry/1.

Examples

iex> child_spec = %{
...>   id: MyHelper,
...>   start: {
...>     Agent,
...>     :start_link,
...>     [fn -> 1 end, [name: Helper.via_registry(MyHelper)]]
...>   }
...> }
iex> :ok = Helper.with_helper(MyHelper, child_spec, fn pid -> Agent.update(pid, & &1 + 1) end)
iex> Helper.with_helper(MyHelper, child_spec, fn pid -> Agent.get(pid, & &1) end)
2