instead of
Map.fetch(params, :shoes)
design patterns
Following Scott Wlaschin’s guidance - use functions!
def fetch_item(map, key) do
case Map.fetch(map, key) do
:error ->
{:error, key}
result ->
result
end
end
...
with(
{:ok, shoes} <- fetch_item(outfit, :shoes),
{:ok, shirt} <- fetch_item(outfit, :shirt),
{true, _} <- {shoes_match_shirt?(shoes, shirt), :matching}
) do
{:ok, "service allowed"}
else
{:error, :shoes} ->
{:error, "you forgot your shoes!"}
_ ->
:error
end
...
or
def fetch_item(map, key, msg) when is_binary(msg) do
case Map.fetch(map, key) do
:error ->
{:error, msg}
result ->
result
end
end
...
with(
{:ok, shoes} <- fetch_item(outfit, :shoes, "you forgot your shoes!"),
{:ok, shirt} <- fetch_item(outfit, :shirt, "you forgot your shirt!"),
{true, _} <- {shoes_match_shirt?(shoes, shirt), :matching}
) do
{:ok, "service allowed"}
else
{:error, msg} = msg_error when is_binary(msg) ->
msg_error
_ ->
:error
end
...
