I am new to elixir and I am trying to get some text from a very nested map.
So I am doing a get request to this link and I am decoding it with Jason.decode.
What I want to do is iterate over it and get every text value (sections->0->content->0->text).
In the end I just want it to be a big string of all the text values
(the link can always change so there might be more maps etc)
Thanks in advance!
You can use Enum with the pipe operator |> to enumerate the data structure and extract the parts you want.
For example:
def pokedex(id) do
HTTPoison.get!("https://pokemon.fandom.com/api/v1/Articles/AsSimpleJson?id=#{id}")
|> Map.get(:body)
|> Jason.decode!()
|> Map.get("sections")
|> Enum.reject(fn %{"content" => content} -> content === [] end)
|> Enum.flat_map(fn %{"content" => content} ->
content
|> Enum.filter(fn %{"type" => type} -> type in ["text", "paragraph"] end)
|> Enum.map(fn %{"text" => text} -> text end)
end)
|> Enum.join("\n")
end
A breakdown:
Map.get("sections") selects the contents of the sections.Enum.reject(...) ignores empty sections.Enum.flat_map iterates over the sections, gets the contents of each section, transforms it using the inner function, and then flatten the result into a single list.
Enum.filter(...) only process contents whose type property is text or paragraph.Enum.map extracts the text property from each contents map.Enum.join joins the resulting list of strings with a newline character.
Elixir provides(through erlang) some functions which can reflect upon the data-structures to check their type like is_map/1, is_list/1, is_number/1, is_boolean/1, is_binary/1, is_nil/1 etc. From docs
Try to go the common data-types you will have in your response. They could be a primitive, map or list of primitives where primitives are like boolean, numeric or a string.
Write a function which tries to recursively go through the data-structure you get until it reaches a primitive and then return the stringifed primitive
Ex. for maps, go through every value(ignore key) and if the value is not a primitive, call the function recursively with that node until you reach a primitive and can return a stringified value. Similar for lists
Something like this should work:
defmodule Test do
def stringify(data) do
cond do
# <> is concatenation operator
# -- call stringify() for every value in map and return concatenated string
is_map(data) -> data |> Map.values |> Enum.reduce("", fn x, acc -> acc <> stringify(x) end)
# -- call stringify() for every element in list and return concatenated string
is_list(data) -> data |> Enum.reduce("", fn x, acc -> acc <> stringify(x) end)
is_boolean(data) -> to_string(data)
is_number(data) -> to_string(data)
is_binary(data) -> data # elixir strings are binaries
true -> ""
end
end
end
# For testing...
{:ok, %HTTPoison.Response{body: sbody}} = HTTPoison.get("https://pokemon.fandom.com/api/v1/Articles/AsSimpleJson?id=2409")
{:ok, body} = Poison.decode(sbody)
Test.stringify(body)
# returns
"Cyndaquil (Japanese: ヒノアラシ Hinoarashi) is the Fire-type Starter..."
If using the external package for this task is an option, you might give a try to the package I wrote for the exactly this purpose: Iteraptor.
It provides iteration/map/reduce functionality over nested Elixir enumerable terms.
