Elixir: best practice to extract data from nested structs

Question

In Elixir we can get data from nested data structures using

data = %{field: %{other_field: 1}}
data[:field][:other_field]

If it contains lists it also can be done using

data = %{field: %{other_field: [1]}}
get_in data, [:field, :other_field, Access.at(0)]

But how to get that data given that data.field.other_field is a structure? Both of the above would fail because structs don't implement Access.fetch/2.

data = %{field: %{other_field: %Struct{a: 1}}}

So what's the right way to access nested structs data other than pattern matching?

Answer 1

Use Access.key/2:

key(key, default \\ nil)

Accesses the given key in a map/struct.

Uses the default value if the key does not exist or if the value being accessed is nil.

iex(1)> defmodule Struct do
...(1)>   defstruct [:a]
...(1)> end
iex(2)> data = %{field: %{other_field: %Struct{a: 1}}}
%{field: %{other_field: %Struct{a: 1}}}
iex(3)> get_in data, [:field, :other_field, Access.key(:a)]
1
iex(4)> get_in data, [:field, :other_field, Access.key(:b, :default)]
:default