I think the syntax might be ambiguous in some edge gases because the keys
on a map can be anything. For example:
iex(1)> map = %{:a => "hello", {:b, [:d]} => 1, :b => %{d: 3}}
%{:a => "hello", :b => %{d: 3}, {:b, [:d]} => 1}
iex(2)> Map.take(map, [:a, b: [:d]])
%{:a => "hello", {:b, [:d]} => 1}
On Wednesday, September 2, 2020 at 2:34:45 PM UTC+2 Samuel Manzanera wrote:
> Another advantage it is the support of dynamic key pattern matching.
> If you are supporting function which accept paramete as the keys to filter
> the map, so it can be dynamically filtered out.
>
> Example
>
> def get_data(fields) do
> get_map_from_state_or_db()
> |> Map.take_in(fields) # or take_in (with Access implementation)
>
> end
> Le mercredi 2 septembre 2020 à 14:30:36 UTC+2, Samuel Manzanera a écrit :
>
>>
>> Hello everybody,
>>
>> I propose the support of Map.take_in/2 to extract values using nested
>> keys (recursively).
>>
>> I think it may be useful when you only want a part of the map -- mostly
>> when its deep nested map (i.e KV stores, DB engines, etc..) to reduce
>> memory footprint with copy and message passing.
>>
>> Example:
>>
>>
>> iex> Map.take_in(%{a: "hello", b: %{c: "hi", d: "hola"}}, [:a, b: [:d]])
>>
>> %{a: "hello", b: %{d: "hola"}}
>>
>> As discussed in the #1029
>> <https://github.com/elixir-lang/elixir/pull/10296> the feature should be
>> extended to Access for both Map and Keyword implementation.
>>
>> To analyse the efficiency regarding pattern matching.
>>
>> But it's a way to resolve the duplication from pattern matching as in
>> this example.
>>
>> iex> %{a: a, b: %{d: d}} = %{a: "hello", b: %{c: "hi", d: "hola"}}
>> iex> %{a: a, b: %{d: d}}
>> %{a: "hello", b: %{d: "hola"}}
>>
>>
>> Thanks :)
>>
>
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