Today I found myself writing the following piece of code source in context:
def from_list(other_users_json_list) do
other_users_json_list
|> reduce_errors(&from_json_hash/1)
end
defp reduce_errors(enumerable, function) do
enumerable
|> Enum.reduce({:ok, []}, fn
{:error, error}, _ -> {:error, error}
{:ok, list}, elem ->
case function.(elem) do
{:ok, elem} -> [elem | list]
{:error, error} -> {:error, error}
end
end)
end
It tries to turn a list of maps that was parsed before from JSON into a list of structs, returning either {:ok, list_of_structs} or {:error, some_validation_error}.
It should stop parsing as soon as the first error is found. However, the only way I know of that propagates an ok/error-tuple through a list of changes is the above, which feels like an awful lot of manual labour and not very idiomatic Elixir-code.
But I cannot be the only one that has faced this type of problem: Are there other idioms of handling these situations?
