Let’s say I have nested map like this : data = %{ gps: %{ lat: 48.857144, lon: 2.340242, altitude: 35.0 }, metadata: %{ payload: %{ content: "1aff4c0002154a080bff4c0010774058308876aa3a29", scantime: 1644362438 } mac…

Here you go: defmodule Example do def sample(acc \\ %{}, data, info) # in case nested value does not exists def sample(acc, nil, _info), do: acc # instead of above you may want to use another code # as it would place a nil value for each nested info who does not exists in data you passe…

What should happen if a value is missing? Is that a case you need to worry about, or is the shape of the payload reliable?

You can also have a look at a library like GitHub - hissssst/pathex: Fastest tool to access data in Elixir · GitHub .

[image] Eiji: This code would automatically pick data you need by simply passing an info. Also if you want to add something to result you simply can pass it as first argument which means that you can call this function multiple times for different data: Works like a charm thank you ! I update…

[image] zatae: An error should be raised. In this case, pattern match! %{ gps: %{ lat: lat, lon: lon, altitude: alt }, metadata: %{ payload: %{ scantime: scantime } receivetime: receive_time, } = data } Pattern matc…

I think I don’t get what you are trying to explain. This is only validating data, right ? How is this going to “flatten” the map ?

The pattern matching is not useful only for validation, but also for assigning variables. Simplest example: iex> %{a: a} = %{a: 5} %{a: 5} iex> a 5 What @benwilson512 suggested is to do exactly same for nested structures, for example: iex> %{nested: %{a: a}, b: b} = %{nested: %{a: 5}, b: 10} %{ne…

I understand now ! Thank you :slightly_smiling_face:

I have another question regarding the solution you gave. Is that possible to have a non nested value at the root of the map? Like this : data = %{ gps: %{ lat: 48.857144, lon: 2.340242, altitude: 35.0 }, macaddress: "B8:C0:78:CD:12:AB" } I am having a hard time finding a way to r…

Sure thing! Look that in original version I’m using map as a root of input, but in code you would find that also list is supported. The proper info for this data would be: data = %{ gps: %{ lat: 48.857144, lon: 2.340242, altitude: 35.0 }, macaddress: "B8:C0:78:CD:12:AB" } info = …

Elixir Programming Language Forum

Most efficient way to retrieve multiple values from nested map

Questions & Help Questions

zatae September 13, 2022, 9:07pm 9

I understand now ! Thank you