hokie81

hokie81

(pretty new to Elixir here…)

sometimes I see:

case [...] do
  {:ok, [...]} -> [...]
  # using _ as default
  {_, other} -> {:error, other}
end

other times:

case [...] do
  {:ok, [...]} -> [...]
  # not using _ as default
  other -> {:error, other}
end

and other times:

case [...] do
  {:ok, [...]} -> [...]
  # using _xxx as default
  _other -> :ok
end

Are these the same thing? If not what are the differences between them and considerations for use of one over the other?

Tyia.

First Post! Switch mode

thomas.fortes

thomas.fortes

Imagine that you have a value response that could be a few things:

response = {:ok, result}
response = {:error, reason}
response = {:invalid, :other, :fields}

Then the cases would be:

# This would work for the first two cases returning result in the first one,
# {:error, other} for the second one and raise an exception for the third one (no match at all).
case response do
  {:ok, result} -> result
  {_, other} -> {:error, other}
end

# This would work for all the cases and return result for the first case,
# {:error, other} for the second case and
# {:error, {:invalid, :other, :fields}} for the third one
case response do
  {:ok, result} -> result
  other -> {:error, other}
end

# This would return result for the first case and :ok for any other response.
case response do
  {:ok, result} -> result
  _other -> :ok
end

Usually you will match a value that comes from a function and the clauses of the match will depend of the format of the result of that function.

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