No function clause matching in Regex.match?/2 on Elixir w/ Phoenix - json

Question

I have a route in Phoenix that needs to check the JSON parameters with REGEX.
In my routine, I am creating a list of errors to report in the body in case one or more regexes fail.
But whenever I run the code, I get the "FunctionClauseError" error on "Regex.match?". I have tried String.match, but they evaluate to the same function.
Here is my code:
def postServidor(conn, parameters) do
reasons = []
error = False
if not Regex.match?(~r/^(19[0-9]{2}|2[0-9]{3})-(0[1-9]|1[012])-([123]0|[012][1-9]|31)$/, Map.get(parameters, "data_nascimento")) do
{error, reasons} = {True, reasons ++ [%{Reason => "[data_nascimento] missing or failed to match API requirements. It should look like this: 1969-02-12"}]}
end
if not Regex.match?(~r/^([A-Z][a-z]+([ ]?[a-z]?['-]?[A-Z][a-z]+)*)$/, Map.get(parameters, "nome")) do
{error, reasons} = {True, reasons ++ [%{Reason => "[name] missing or failed to match API requirements. It should look like this: Firstname Middlename(optional) Lastname"}]}
end
if not Regex.match?(~r/^([A-Z][a-z]+([ ]?[a-z]?['-]?[A-Z][a-z]+)*)$/, Map.get(parameters, "nome_identificacao")) do
{error, reasons} = {True, reasons ++ [%{Reason => "[nome_identificacao] missing or failed to match API requirements. It should look like this: Firstname Middlename(optional) Lastname"}]}
end
if not Regex.match?(~r/\b[MF]{1}\b/, Map.get(parameters, "sexo")) do
{error, reasons} = {True, reasons ++ [%{Reason => "[sexo] missing or failed to match API requirements. It should look like this: M for male, F for female"}]}
end
if not Regex.match?( ~r/\b[0-9]+\b/, Map.get(parameters, "id_pessoa")) do
{error, reasons} = {True, reasons ++ [%{Reason => "[id_pessoa] missing or failed to match API requirements. It should be numeric. "}]}
end
if not Regex.match?(~r/\b[0-9]+\b/, Map.get(parameters, "matricula_interna")) do
{error, reasons} = {True, reasons ++ [%{Reason => "[matricula_interna] missing or failed to match API requirements. It should be numeric. "}]}
end
if not Regex.match?(~r/\b[0-9]+\b/, Map.get(parameters, "siape")) do
{error, reasons} = {True, reasons ++ [%{Reason => "[siape] missing or failed to match API requirements. It should be numeric. "}]}
end
if error = True do
json put_status(conn, 400),reasons
else
IO.puts("ok")
end
end

Answer 1

Regex.match?/2 requires a string as its second argument. You're using Map.get/3 to potentially return that string, but if the key isn't found in the map, it defaults to nil, and that's my guess as to what's happening. If the key is not found in your map, it's passing nil to Regex.match?/2, for which there will be no function clause that matches. You can either fix your map to correctly have the key, or you can provide your own default string to use as a third parameter to Map.get/3. For example, Map.get(parameters, "data_nascimento", "some default").