TylerPachal

# This an example of how a runtime exception inside of a flow
# sends a :normal exit message.
#
# To run this code add the Flow dependency to the mix.exs file:
# {:flow, "~> 0.11"}
#
# The behaviour that I get is the stacktrace is printed to STDOUT,
# and the flush() function outputs a message like this:
# {:EXIT, #PID<0.144.0>, :normal}
# But I am expecting a non-normal exit message.

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# Pattern matching with a case statement
my_bool = case my_map do
  %{foo: _, bar: _} -> true
  _ -> false
end

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# Pattern matching with Kernel.match?/2
my_bool = match?(%{foo: _, bar: _}, my_map)

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# Using match?/2 with a guard statement
user = User.find(123)
can_access = match?(%{role: r, name: "tyler"} when r in ["owner", "admin"], user)
if can_access do
  # 200
else
  # 403
end

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# You don't always need pattern matching
is_admin = Map.get(user, "is_admin") || false

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def application do
  [
    extra_applications: [:logger, :inets],
    mod: {MyModule, []}
  ]
end

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def init(:ok) do
  children =
    [
      kafka_producer_spec(),
      kafka_consumer_spec(),
      other_thing_spec(),
      Api # Start the Api from the child_spec() function defined in that module
    ]
    end

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defmodule Api do
  require Record

  # Wrap the Erlang Record to make the request_uri parameter easier to access
  Record.defrecord :httpd, Record.extract(:mod, from_lib: "inets/include/httpd.hrl")

  def child_spec(_) do
    opts = [
      server_name: 'Api', 
      server_root: '/tmp',

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with {:ok, width}  <- Map.fetch(opts, :width),
     {:ok, height} <- Map.fetch(opts, :height)
do
  {:ok, width * height}
else
  :error -> {:error, :wrong_data}
end

TylerPachal

with {:width, {:ok, width}}   <- {:width, Map.fetch(opts, :width)},
     {:height, {:ok, height}} <- {:height, Map.fetch(opts, :height)}
do
  {:ok, width * height}
else
  {:width, :error} -> {:error, :missing_width}
  {:height, :error} -> {:error, :missing_height}
end