Elixir Working with Json API

In this post you will learn the following:

• The best libraries to work with API JSON in elixir
• How to decode and fetch data from the JSON response

For this tutorial am going to use JSON from this amazing website (http://www.icndb.com/api/) to fetch random funny jokes.I have used this API because it is somehow configurable to include your names.In case you want to use another service I highly recommend looking for one at this Github repo(https://github.com/toddmotto/public-apis).
Now lets create a new elixir project by writing the following on the terminal

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1	mix new joker

The above command will create an elixir project called joker.
Now open your mix.exs and then add these two libraries in deps function.

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defp deps do   [     {:httpoison, "~> 1.0"},     {:json, "~> 1.0"}   ] end

After adding the above libraries download them to your project by typing mix deps.get on your terminal and also add :httpoison to your list of applications. ie

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def application do     [       extra_applications: [:logger, :httpoison]     ]   end

:httpoison, will be used to fetch JSON data from the above API and then we will use :json to convert that JSON into an Elixir Map in order to access the items as key values. To learn more about these libraries visit their respective Github repositories.

• https://github.com/cblage/elixir-json
• https://github.com/edgurgel/httpoison

Now let write some code, here am going to share the full code then I will explain every function in it.

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defmodule Joker do   @joke_server "http://api.icndb.com/jokes/random"     def get_joke(your_name) do     result =       your_name       |> split_name       |> build_url       |> fetch_decode_json       case result do       {:ok, joke} ->         IO.puts(joke)         :error ->         IO.puts("An error occurred while fetching a random joke.")     end   end     def split_name(name) do     name     |> String.split(" ")     |> Enum.take(2)   end     def build_url([first, second | []]) do     "#{@joke_server}?firstName=#{URI.encode(first)}&lastName=#{second}"   end     def build_url([first | []]) do     "#{@joke_server}?firstName=#{URI.encode(first)}"   end     def fetch_decode_json(url) do     url |> HTTPoison.get() |> decode_json   end     def decode_json({:ok, %HTTPoison.Response{body: body, status_code: 200}}) do     case JSON.decode(body) do       {:ok, json_map} ->         joke = json_map |> get_in(["value", "joke"])         {:ok, joke}         _ ->         :error     end   end     def decode_json(_) do     :error   end end

The main entry point of the above module is get_joke function, here you provide either your first name or both of your names. When you provide the name the text will be piped to split_name where the text is split into a list of words by String.split. If you just provide a single name, only one item will be stored in the list.
After the name is converted into a list of words we pipe it to build_url function where we use pattern matching to build an Url of the name depending or the number of names given.
Now let pipe the built url to fetch_decode_json where its content is fetched from the internet using HTTPoison.get(your_url), once the data is returned we use pattern matching to either return an :error atom or convert the JSON into a map that we can work with easily. The JSON will be converted into a map using the JSON.decode(your_json_here). To get the desired item from the nested map am using get_in function that is cleaner to use when compared to a method like this one.

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1	joke = json_map["value"]["joke"]

After data is returned from fetch_decode_json, we use case function to match the results and return them to the console.

TIPS: when working with data in Elixir

• Use iex -S mix, to run the functions you have written in order to know what data it was returned so that you can write the correct pattern to match it.
  ie
  
  
• Use an editor with helper plugins to minimize errors.In my case am using Atom Editor

Exercise

• Use this site to fetch and display data. https://jsonplaceholder.typicode.com/. If you experience any issue post it on the comment section bellow so that I can help.

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