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Best use cases for 'with' in elixir
defmodule Bicycle do
defstruct [wheels: 2, pedals: nil, seat: nil, pass: nil]
end
defmodule BikeTypeCheck do
def check(%Bicycle{wheels: count, pedals: val}=bike) do
return = with {:ok, 2} <- count_wheels(count),
{:ok, true} <- has_pedals(val),
do: pedal_away(bike)
keep_passing_msg = fn
{:error, :motorbike} -> handle_motor_bike(bike)
{:error, :tricycle} -> handle_tricycle(bike)
answer -> IO.inspect(answer)
end
return |> keep_passing_msg.()
end
defp count_wheels(2), do: {:ok, 2}
defp count_wheels(3), do: {:error, :tricycle}
defp count_wheels(_), do: {:error, :not_bike}
defp has_pedals(true), do: {:ok, true}
defp has_pedals(_), do: {:error, :motorbike}
defp pedal_away(bike) do
IO.puts "\nONLY TRUE BIKE."
%{bike | pass: true}
end
defp handle_motor_bike(bike) do
IO.puts "\nSend Motorbike somewhere."
<>"\nscope captured maintained within function its defined?"
IO.inspect(bike)
end
defp handle_tricycle(bike) do
IO.puts "\nSend Tricycle somewhere.\n"
<>"scope captured maintained within function its defined?"
IO.inspect(bike)
end
end
bike = struct(Bicycle, pedals: true, wheels: 2)
bike2 = struct(Bicycle, pedals: false, wheels: 2)
bike3 = struct(Bicycle, pedals: false, wheels: 3)
# Keep passing allong the message
# keep_passing_msg = fn
# {:error, :motorbike} -> IO.inspect(error)
# answer -> IO.inspect(answer)
# end
BikeTypeCheck.check(bike) #|> keep_passing_msg.()
BikeTypeCheck.check(bike2) #|> keep_passing_msg.()
BikeTypeCheck.check(bike3) #|> keep_passing_msg.()
val = %{height: 10, width: 100, length: 5}
work = fn(opts) ->
result =
with {:ok, w} <- Map.fetch(opts, :width),
{:ok, h} <- Map.fetch(opts, :height),
{:ok, l} <- Map.fetch(opts, :length),
do: h * w * l
result
|> case do
:error -> "Not full match"
val -> val
end
end
IO.puts work.(val)
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