How to map multi level json

What do you mean by “map” here?

map the keys and values from the response so that I can call it in template. Specifically to a table.

Map to what exactly, what shape of data do you want? If you want to decode a json object into an elixir map, you can use a json decoder, there are several.

The most popular is probably GitHub - devinus/poison: An incredibly fast, pure Elixir JSON library · GitHub, with it your code would be like this:

resp = HTTPoison.get!(url)
json = Poison.decode!(resp)

Here, json is an elixir term, probably a map. So you’d be able to use it to populate your table.

I was able to decode the response using poison.decode and now, my goal is decode the two-level json (you can see my example from the previous posts) and pass it to my template. I’m only having difficulty on how can I decode a multi-level json and be able to pass it on a template

You can’t do that directly, because you have list there. I will give you 4 example ways to achieve what you need:

1. Get first item using List.first/1 or last item using List.last/1
2. Get by specified index using Enum.at/2
3. Iterate over list and do something for every item in it using Enum.each/2 or Enum.map/2 (depends on what you need).
4. Find element which is interesting for you by using Enum.find/2

For example:

list = Poison.decode!(response.body)
first_item = List.first(list)
last_item = List.last(list)
n = 10
nth_item = Enum.at(list, n) # where n is integer
found_item = Enum.find(list, & &1["Payor"] == "ASMSI")

# Then you can fetch specified data as you wanted:
%{"InvoiceDetails" => invoicedetails} = first_item
%{"InvoiceDetails" => invoicedetails} = last_item
%{"InvoiceDetails" => invoicedetails} = nth_item
%{"InvoiceDetails" => invoicedetails} = found_item

# Or do something for every item in list

defmodule Example do
  def sample_each(list), do: Enum.each(list, &do_sample_each/1)

  defp do_sample_each(%{"InvoiceDetails" => invoicedetails}), do: IO.inspect(invoicedetails)

  def sample_map(list), do: Enum.map(list, &do_sample_map/1)

  defp do_sample_map(%{"InvoiceDetails" => invoicedetails}), do: invoicedetails
end

:ok = Example.sample_each(list) # debugs "InvoiceDetails" for every item
invoicedetails_list = Example.sample_map(list) # returns list of invoicedetails

Thank you for the effort. I greatly appreciate it and it serves as an additional knowledge for me. But it seems, my explanation is unclear. What I pursue is to be able to pass the first level of the json as well as the second level as values going through to my template and to be displayed on table. I visualize it like a double for loop in other language. So I’m gonna use all the data from my json response.

I’m planning to use the json data to a jquery datatable with a expand and collapse rows. For example, I’ll be displaying the first level json on collapsed rows and upon expanding the row, the second level json (Invoice details) will show

You should probably post the data as you visualize it in its final shape then. In other words, what do you expect to get from the json list you posted in OP?

mymap = Poison.decode!(response.body)

In your example you’re extracting a single thing from what decode returns, and it sounds like you simply want the whole thing.

Let’s say I have a template like this:

    <table>
    <%= for dataFirst <- @FirstLevelJson do %> #this is the first level of my json response (first for loop)
    <tr> #first table row which will be collapsed row which also contains my first level from my json
    <td><%= dataFirst["Payor"] %></td>
    <td><%= dataFirst["RevenueSource"] %></td>
    <td><%= dataFirst["DateCreated"] %></td>
    </tr>
<tr>
<table>
  <%= for dataSecond <- @SecondLevelJson do %> #this is the second level of my json response (second for-loop or the _InvoiceDetails_)
   <tr> #second table row which will be the expanded row which contains the second level (InvoiceDetails)
    <td><%= dataSecond["TransactionDetails"] %></td>
    <td><%= dataSecond["TransCount"] %></td>
    <td><%= dataSecond["Rate"] %></td>
    <td><%= data["Total"] %></td>
  <td><%= data["Vat"] %></td>
  <td><%= data["Vatable"] %></td>
  <td><%= data["TotalAmount"] %></td>
    </tr>
 <% end %>
</table>
</tr>
    <% end %>
    </table>

and on my controller:

%{"FirstLevelJson" => FirstLevelJson, "SecondLevelJson" => SecondLevelJson} = Poison.decode!(response.body) #I don't know if this is possible. That's why I'm asking for help if there's a way to pass this to my template
render(conn, "mytemplate.html", FirstLevelJson: FirstLevelJson, SecondLevelJson: SecondLevelJson)

Here’s what I’m trying to achieve:

image1221×435 18.7 KB

(picture from: https://www.jqueryscript.net/demo/jQuery-Plugin-For-Expandable-Bootstrap-Table-Rows/)

Quit fighting against the structure you get, just use it instead, like:

data = Poison.decode!(...)

for dataFirst <- data

for dataSecond <- dataFirst["whatever"]

That’s assuming that the JSON you get is encoded nested the same as what you’re trying to display, something like:

[{"obj": {"details": {...}, ...}, ...]

(Regardless of how it’s structured, any pattern match that directly pulls out only a portion from decode cannot be what you want. You have to get it all.)

If there were only item, you can match nested stuff:

[%{obj: {details: mySecondLevel}} = myTopLevel]

But I don’t think that’s what you want.