Created
November 1, 2019 11:48
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`MapAccess.filter/1` → the same as `Access.filter/1`, but works with maps.
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defmodule MapAccess do | |
@spec filter((term -> boolean)) :: Access.access_fun(data :: map, get_value :: map) | |
def filter(func) when is_function(func, 1) do | |
fn op, data, next -> filter(op, data, func, next) end | |
end | |
defp filter(:get, %{} = data, func, next) do | |
data |> Enum.filter(func) |> Enum.map(next) |> Map.new() | |
end | |
defp filter(:get_and_update, %{} = data, func, next) do | |
get_and_update_filter(Map.to_list(data), func, next, [], []) | |
end | |
defp filter(_op, data, _func, _next) do | |
raise "MapAccess.filter/1 expected a map, got: #{inspect(data)}" | |
end | |
defp get_and_update_filter([{k, v} = head | rest], func, next, updates, gets) do | |
if func.(head) do | |
case next.(v) do | |
{get, update} -> | |
get_and_update_filter(rest, func, next, [{k, update} | updates], [head | gets]) | |
:pop -> | |
get_and_update_filter(rest, func, next, updates, [head | gets]) | |
end | |
else | |
get_and_update_filter(rest, func, next, [head | updates], gets) | |
end | |
end | |
defp get_and_update_filter([], _func, _next, updates, gets) do | |
{Map.new(gets), Map.new(updates)} | |
end | |
end | |
input = %{ | |
payload: %{ | |
"foo" => 42, | |
"bar" => 5, | |
"baz" => 10 | |
} | |
} | |
filter_fun = MapAccess.filter(&match?({"b" <> _, _}, &1)) | |
update_fun = &(&1 * 2) | |
get_and_update_in_fun = &{&1, &1 * 2} | |
get_in(input, [:payload, filter_fun]) | |
# ⇒ %{"bar" => 5, "baz" => 10} | |
put_in(input, [:payload, filter_fun], 42) | |
# ⇒ %{payload: %{"bar" => 42, "baz" => 42, "foo" => 42}} | |
update_in(input, [:payload, filter_fun], update_fun) | |
# ⇒ %{payload: %{"bar" => 10, "baz" => 20, "foo" => 42}} | |
get_and_update_in(input, [:payload, filter_fun], get_and_update_in_fun) | |
# ⇒ {%{"bar" => 5, "baz" => 10}, | |
# %{payload: %{"bar" => 10, "baz" => 20, "foo" => 42}}} | |
pop_in(input, [:payload, filter_fun]) | |
# ⇒ {%{"bar" => 5, "baz" => 10}, %{payload: %{"foo" => 42}}} |
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