How to make API calls in Rails

I'll be using OpenWeather API in the below examples.

Let's get started by creating a new rails app.

rails new weather-app

Install Faraday

Faraday is used to make HTTP requests to API
Add this line to the top of your application's Gemfile:

gem 'faraday'

Execute:

bundle

Generate Controller & View for making API requests

rails g controller search index

Now open /config/routes.rb and replace get 'search/index' with:

get '/search' => 'search#index', :as => 'search'

We'll be making API requests using this route and also display response on browser on the same route.

Open /app/views/search/index.html.erb and fill it with:

<h2>Search for world weather by location</h2>

<%= form_with(url: search_path, method: "get", local: true) do %>
  <%= label_tag(:location, "Enter Location name:") %>
  <%= text_field_tag(:location) %>
  <%= submit_tag("Search") %>
<% end %>

<% if @response %>
  <div>
    <%= @response.body %>
  </div>
<% end %>

Which gives us a form to enter a location whose weather data we can pull from OpenWeather. And in if statement we have @response variable which is set to response from API if we made a call in the controller.

Create API service

Now let's actually get into the process of making API request to OpenWeather.
Although we have Faraday installed, it can't be directly called from within the controller.
Create a new folder named services inside /app. Make sure not to change the name of the folder.
Next add a ruby file in /app/services, this file can be named anything you wish but the same name albeit capitalized should be used for the module inside it.

I'll create openweather.rb inside /app/services

module Openweather
  class Search
    def self.by_location(location)
      Faraday.get 'https://api.openweathermap.org/data/2.5/weather?q=' + location + '&appid=' + ENV['API_KEY']
    end
  end
end

The class inside the module and the method inside the class can be named anything.

From the code above, we can make out that - by calling Openweather::Search.by_location method with a location parameter would make an API call to OpenWeather, but what about ENV['API_KEY']?
We sure can replace ENV['API_KEY'] with actual API key provided by OpenWeather, but leaving an API key within code is not right. So, we are going to place our API key as an Environment variable.
First let's place API key as Environment variable in our local machine.
To do this we'll be using Dotenv gem

Install Dotenv

Add this line to the top of your application's Gemfile:

gem 'dotenv-rails', groups: [:development, :test]

And then execute:

bundle

Now add a file named .env to the root of your application. Make sure not to change the name of the file. Add your API key in the first line like so:

API_KEY=your_api_key

Replace your_api_key with your actual key provided by OpenWeather.
If your going to commit your work add .env file to .gitignoreso that it is not tracked by git.

Call API service from the controller

Now for the final part, add this to index action of your controller /app/controllers/search_controller.rb

if params['location']
  @response = Openweather::Search.by_location(params['location'])
end

Make sure match the names of module, class and function that you named earlier.

Check the result

Now, open the server

rails server

And visit http://localhost:3000/search from your browser.
Search for a location to see the response.

Comments

[GarnicaJR]

Nice tutorial, thanks