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Elixir / Processes and Messages

GenServer calls

Learn GenServer calls in Elixir through a focused explanation, a dedicated topic-specific example, an engineering boundary, and a mastery check.

12 min read • Intermediate

GenServer calls is a focused Elixir lesson inside Processes and Messages. The example uses the construct named in the lesson directly rather than reusing a generic placeholder.

Trace the example from its inputs through GenServer calls and identify the behavior that would change if that construct were removed or replaced. Pay attention to the language-specific rules shown by the syntax, because neighboring lessons intentionally exercise different mechanisms.

Topic-specific example

elixir-0059-16b0d49f51.exs
elixir Try It Live 
defmodule Counter do
  use GenServer
  def start_link(v), do: GenServer.start_link(__MODULE__, v)
  def init(v), do: {:ok, v}
  def handle_call(:get, _from, v), do: {:reply, v, v}
end
Edge case / engineering note

For GenServer calls, test one realistic boundary: empty data, invalid input, unavailable resources, lifetime/cleanup, type constraints, or concurrency timing where applicable. A successful happy path is not enough to prove the construct is used correctly.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

GenServer calls Mastery Check →
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GenServer casts