CODEWITHSUNDEEP
exceptionerror-handlingelixir
polonio
polonio

Reputation: 351

Handling Errors - Elixir

I have a simple function like this:

  def currencyConverter({ from, to, amount }) when is_float(amount) do
    result = exchangeConversion({ from, to, amount })
    exchangeResult = resultParser(result)
    exchangeResult
  end

I want to guarantee that from and to are strings and amount are float, and if not, display send a customize error message instead erlang error What's the best way to do this?

Upvotes: 0

Views: 283

Answers (1)

Julio GB
Julio GB

Reputation: 447

you can make two functions with same name and arity, one with guards and one without

def currencyConverter({from, to, amount}) when is_float(amount) and is_bitstring(to) and is_bitstring(from) do
  result = exchangeConversion({ from, to, amount })
  exchangeResult = resultParser(result)
  exchangeResult
end
def currencyConverter(_), do: raise "Custom error msg"

If you want to check the input type, you will need to create a function to do it because elixir does not have a global one.

def currencyConverter({from, to, amount}) when is_float(amount) and is_bitstring(to) and is_binary(from) do
  result = exchangeConversion({ from, to, amount })
  exchangeResult = resultParser(result)
  exchangeResult
end
def currencyConverter({from, to, amount}) do
 raise """
   You called currencyConverter/1 with the following invalid variable types:
   'from' is type #{typeof(from)}, need to be bitstring
   'to' is type #{typeof(to)}, need to be bitstring
   'amount' is type #{typeof(amount)}, need to be float
 """
end

def typeof(self) do
        cond do
            is_float(self)    -> "float"
            is_number(self)   -> "number"
            is_atom(self)     -> "atom"
            is_boolean(self)  -> "boolean"
            is_bitstring(self)-> "bitstring"
            is_binary(self)   -> "binary"
            is_function(self) -> "function"
            is_list(self)     -> "list"
            is_tuple(self)    -> "tuple"
            true              -> "ni l'un ni l'autre"
        end    
end

(typeof/1 function is based on this post:https://stackoverflow.com/a/40777498/10998856)

Upvotes: 1

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