rrmartins
Hello,
I came to make a provocation about a way of writing code.
I’m writing a small private project to shorten urls and I came across a change in the writing of a case.
I saw that when writing the case in my function I felt that the function seemed complex to understand and read. I thought about changing the case to use Pattern Matching of the functions.
leaving this code:
defp validate_url(changeset, field, opts \\ []) do
validate_change(changeset, field, fn _, value ->
case URI.parse(value) do
%URI{scheme: nil} ->
"is missing a scheme (e.g. https)"
%URI{host: nil} ->
"is missing a host"
%URI{host: host} ->
case :inet.gethostbyname(Kernel.to_charlist(host)) do
{:ok, _} -> nil
{:error, _} -> "invalid host"
end
end
|> case do
error when is_binary(error) -> [{field, Keyword.get(opts, :message, error)}]
_ -> []
end
end)
end
for this:
defp validate_url(changeset, field, opts \\ []) do
validate_change(changeset, field, fn _, value ->
value
|> URI.parse()
|> handle_parse()
|> handle_error_parse()
end)
end
defp handle_error_parse(error) when is_binary(error), do: [{field, Keyword.get(opts, :message, error)}]
defp handle_error_parse(_), do: []
defp handle_parse(%URI{scheme: nil}), do: "is missing a scheme (e.g. https)"
defp handle_parse(%URI{host: nil}), do: "is missing a host"
defp handle_parse(%URI{host: host}) do
host
|> Kernel.to_charlist()
|> :inet.gethostbyname()
|> handle_hostbyname()
end
defp handle_hostbyname({:ok, _}), do: nil
defp handle_hostbyname({:error, _}), do: "invalid host"
I’m preferring to use Pattern Matching instead of case and other control flow structures.
what do you think?
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stefanchrobot
I personally prefer
caseover multiple function heads (sidenote: both use pattern matching!). But I’d do this:sodapopcan
This is one of those cases of “Which do you prefer?” Your answer to that is the right one
Personally I prefer multi-head functions whenever it’s possible, but that’s just me. I maybe wouldn’t start every function name with
handle_as it feels a bit noisy but, again, that’s just me.sodapopcan
PS, pattern matching essentially is control flow (among other things). It’s right there on the Erlang homepage
Last Post!
cjbottaro
I am on the fence on this one. Sometimes I think the code is cleaner looking with a single function head that has a single case statement…
Especially if the function has other heads that deal with other things. Sometimes the combinatory explosion flatting is just too much.