About

While Elixir programmers often say “let it crash” and code for the “happy path”, there are often times we need to rescue the function call to return a specific value, message or release system resources.

• Functions that raise errors under normal circumstances should have ! at the end of their name.

• Functions may alternatively return atoms and tuples to indicate success and failure:

  Map.fetch(%{a: 1}, :a)
  # => {:ok, 1}
  Map.fetch(%{a: 1}, :b)
  # => :error
  
  Map.fetch!(%{a: 1}, :b)
  # => raises KeyError

Avoid anti-patterns

Avoid programming patterns that use errors to control logical flow. This is an anti-pattern in Elixir.

# Avoid using errors for control-flow.
try do
  {:ok, value} = MyModule.janky_function()
  "All good! #{value}."
rescue
  e in RuntimeError ->
    reason = e.message
    "Uh oh! #{reason}."
end

# Rather, use control-flow structures for control-flow.
case MyModule.janky_function() do
  {:ok, value} -> "All good! #{value}."
  {:error, reason} -> "Uh oh! #{reason}."
end

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Originally from Exercism elixir concepts