Phoenix路由中Regex.match?/2触发FunctionClauseError问题求助

我来帮你搞定这个问题，你遇到的FunctionClauseError主要是几个细节没注意到，咱们一步步修正：

问题根源 #

1. Elixir布尔值是小写的：你用了大写的True/False，这在Elixir里会被当作自定义原子，不是标准布尔值，直接导致逻辑判断完全出错。
2. 未处理nil参数：当请求里缺少某个参数时，Map.get会返回nil，而Regex.match?/2要求第二个参数必须是字符串，传nil直接触发函数子句错误。
3. 赋值与判断搞混：if error = True是赋值操作，不是相等判断，这会导致无论有没有错误都会进入错误分支。
4. 键名格式错误：%{Reason => "..."}里的Reason是大写开头的原子，不符合Elixir命名规范，返回JSON时也会出现大写键，通常我们用小写的:reason更合理。

修正后的代码 #

def postServidor(conn, parameters) do
  reasons = []
  error = false

  # 校验data_nascimento
  data_nascimento = Map.get(parameters, "data_nascimento")
  unless is_string(data_nascimento) and Regex.match?(~r/^(19[0-9]{2}|2[0-9]{3})-(0[1-9]|1[012])-([123]0|[012][1-9]|31)$/, data_nascimento) do
    reasons = reasons ++ [%{reason: "[data_nascimento] missing or failed to match API requirements. It should look like this: 1969-02-12"}]
    error = true
  end

  # 校验nome
  nome = Map.get(parameters, "nome")
  unless is_string(nome) and Regex.match?(~r/^([A-Z][a-z]+([ ]?[a-z]?['-]?[A-Z][a-z]+)*)$/, nome) do
    reasons = reasons ++ [%{reason: "[nome] missing or failed to match API requirements. It should look like this: Firstname Middlename(optional) Lastname"}]
    error = true
  end

  # 校验nome_identificacao
  nome_identificacao = Map.get(parameters, "nome_identificacao")
  unless is_string(nome_identificacao) and Regex.match?(~r/^([A-Z][a-z]+([ ]?[a-z]?['-]?[A-Z][a-z]+)*)$/, nome_identificacao) do
    reasons = reasons ++ [%{reason: "[nome_identificacao] missing or failed to match API requirements. It should look like this: Firstname Middlename(optional) Lastname"}]
    error = true
  end

  # 校验sexo
  sexo = Map.get(parameters, "sexo")
  unless is_string(sexo) and Regex.match?(~r/\b[MF]{1}\b/, sexo) do
    reasons = reasons ++ [%{reason: "[sexo] missing or failed to match API requirements. It should look like this: M for male, F for female"}]
    error = true
  end

  # 校验id_pessoa
  id_pessoa = Map.get(parameters, "id_pessoa")
  unless is_string(id_pessoa) and Regex.match?(~r/\b[0-9]+\b/, id_pessoa) do
    reasons = reasons ++ [%{reason: "[id_pessoa] missing or failed to match API requirements. It should be numeric."}]
    error = true
  end

  # 校验matricula_interna
  matricula_interna = Map.get(parameters, "matricula_interna")
  unless is_string(matricula_interna) and Regex.match?(~r/\b[0-9]+\b/, matricula_interna) do
    reasons = reasons ++ [%{reason: "[matricula_interna] missing or failed to match API requirements. It should be numeric."}]
    error = true
  end

  # 校验siape
  siape = Map.get(parameters, "siape")
  unless is_string(siape) and Regex.match?(~r/\b[0-9]+\b/, siape) do
    reasons = reasons ++ [%{reason: "[siape] missing or failed to match API requirements. It should be numeric."}]
    error = true
  end

  if error == true do
    conn |> put_status(400) |> json(reasons)
  else
    IO.puts("ok")
    # 补充正常响应，Phoenix路由必须返回conn
    conn |> json(%{status: "ok"})
  end
end

关键改动说明 #

• 把所有True/False替换成Elixir标准的小写true/false
• 每个校验前先通过is_string/1检查参数是否存在且是字符串，避免传nil给Regex.match?
• 把if not ...改成更符合Elixir习惯的unless ...，逻辑更直观
• 修正错误分支的判断条件：用error == true代替error = true，避免误赋值
• 把错误信息的键改成:reason，返回JSON时会自动转成小写的"reason"，符合API规范
• 补充了正常分支的响应（原来的IO.puts仅在控制台打印，Phoenix路由必须返回conn对象）

内容的提问来源于stack exchange，提问作者Auyer