Rails Scaffold API & CRA (Create React App)

Rails API

Lesson Objectives

After this lesson, students will be able to:

Set up a basic Rails API server using scaffold
Set up another server to consume that API using React
Configure CORS to allow Cross Origin Resource Sharing

Why make a Rails API?

Today, we will add a frontend to our Rails API back end.

screenshot

We are providing a service that either ourselves or others will be able to access. Our service happens to be data, in JSON format.

Rails APIs are used as backends for mobile apps as well as desktop apps.

Without a frontend component, the data is its own thing. There is a complete separation of concerns between the data and the display because they are running on separate servers.

You swap out any old display and you should not need to change a single thing on the backend.

Rails server is API only

We will leave our Rails server untouched by any frontend code. It will just serve JSON.

We will then create another app to consume the API, as if we were some other developer or team whose job is just to make the frontend.

What we will be doing

We will review the steps for creating a Rails API for our backend, and serve an index endpoint.
We will create a new app separate from our Rails server for our frontend.
We will use our frontend app to consume the API coming from the backend. Our frontend server will serve React.

Two Apps

Let's start a project that will use two apps

Rails App (our backend): provides the API

React App (our frontend): consumes the API

Setup

Download the starter code, you'll get a folder from the .zip file called noticeboard_app - go ahead and cd into noticeboard_app.

The directory noticeboard_app will contain both our Rails server and our Create React App (noticeboard_client is our Create React app that has some starter code).

Inside this directory we will put both our apps - the front-end (client) and back-end (api AKA server).

We are only putting them together in here to keep them organized. Make sure you open each one in a separate VS Code window, and each one has it's own separate git repo. WARNING: Do not create a git repo in the noticeboard_app folder or you will have deployment issues.

These 2 separate apps can exist on separate systems (that is the point).

Create our Apps

Inside noticeboard_app make the rails api called noticeboard_api:

Remember to add flags for

api option --api
database option -d postgresql
skip active storage option --skip-active-storage (this is some extra stuff that assists with uploading photos and other media/large files to a service like S3 or Amazon Cloud services)
rails new noticeboard_api --api -d postgresql --skip-active-storage

Tree structure: The noticeboard_app directory contains both the _api and _client directories.

Open each child folder (noticeboardapi, and noticeboardclient) in a separate window of your text editor.

If you would like help keeping each window separate so you remember which is which, download the Peacock VS Code extension. It lets you give each window a different color.

Scaffold the Rails API

Let's see how fast we can make our Rails API. (Aim: 15 minutes with explanations)

This morning, we will use the generate scaffold command to generate boilerplate code for a given resource.

Our app will be a noticeboard, and the resource will be notices.

First, go into the Rails directory (the _api one) on the command line.
Then, create the database. rails db:create
Scaffold the resource:

rails g scaffold notice title author phone

rails g scaffold model_name column column column

GOTCHA - do not name the model the same as your app name: ie do not name this app notices and also name your model notices - bad errors will happen!

This will generate all the folders, files, and code needed for a model called Notice that has columns for title, author, and content, all of datatype string.

String is the default datatype.

screenshot

What did "generate scaffold" do?

Created files for migration, model, controller, and routes

db/migrate. Scaffold has created a migration file for our Notice resource. There is a boilerplate method for creating the notices table. Title, author, and phone columns (strings) are ready to go.
app/models/notice.rb. Scaffold has created a file our Notice resource. The model has been set up for us.
Look in config/routes. Scaffold has set our resources for us. The rails routes command will tell us what controllers and actions we should use:

 Prefix Verb   URI Pattern            Controller#Action
notices GET    /notices(.:format)     notices#index
        POST   /notices(.:format)     notices#create
 notice GET    /notices/:id(.:format) notices#show
        PATCH  /notices/:id(.:format) notices#update
        PUT    /notices/:id(.:format) notices#update
        DELETE /notices/:id(.:format) notices#destroy

notices_controller.rb. Scaffold has provided all of the relevant routes for our CRUD actions: index, show, create, update, and delete.
Scaffold has placed instance variables such as @notices = Notice.all for scoping.
There is a new helper method set_notice invoked with a before_action method. All it does is find a notice according to its id before specific routes are hit. It is configured to work only for the show, update, and destroy methods.
In the create method, location is an option for redirecting the page by setting the Location option in the response object. We probably just want the JSON and don't want our server to try to perform a redirect on the client, which can cause errors in Postman, etc. If you run into errors, remove location: @notice from the create action.
Otherwise, the controller file is functionally exactly the same as what we have seen before.

Migrate

Scaffolding does not interact with the database (for good reason).

Remember, all these Ruby migration commands are methods. If we add parens, they will still work the same.

  def change
    create_table(:notices) do |t|
      t.string(:title)
      t.string(:author)
      t.string(:phone)

      t.timestamps
    end
  end

Run the migration: rails db:migrate

Seed

Inside the Gemfile include Faker

gem 'faker'

screenshot

Install the gem with bundle (shorthand for bundle install. install is the default option for the bundle command).

In seeds.rb use Faker to fill out the fields:

100.times do
  Notice.create(
    title: Faker::TvShows::TwinPeaks.quote,
    author: Faker::Movies::StarWars.character,
    phone: Faker::PhoneNumber.cell_phone
  )
end

puts "Seeded database"

Seed with rails db:seed
Run the server with rails s
Check out your API at localhost:3000/notices

screenshot

And we're DONE with our Scaffold!

React Frontend

Remember, our Rails API is just that, an API. Our Rails server is like a data farm. This data farm can be made accessible to any client or platform.

For now, we are done with our API. Let's make a frontend that can interact with it.

Keep your Rails server running.
On the command line, open a new tab. Exit the Rails directory into the parent noticeboard_app.
We are going to make a separate client as our front end. It's not unusual to do so. Imagine a large company like facebook and all the data they manage. They have both a desktop app and a mobile app. These apps share the same databases. It would be a lot of duplication to copy all the data over from the desktop to mobile and then update everything everywhere.

In the interest of time, we are going to start with some boilerplate code:

enter the noticeboard_client folder
npm install
npm start - you may have a conflicting port with your rails app, choose another port when prompted.

Create React App

Create React App does a few really nice things for us. It builds us an app that is tailored to our needs. It does 'hot-reloading' - every time we save we see our changes in the browser update. It also does testing for us and give us helpful messages in the browser console.

Like Rails, Create React App is a bit magical and will handle a lot of things for us behind the scenes. As you continue to grow as developers, you can explore what the different parts of create react app are doing. For now, we'll focus on building something that interacts with our Rails backend.

create react app file structure

Remember, we could use any frontend library or framework. (At least, one that can work with HTTP requests). But we'll stick with React since we've used it before.

React Setup

We'll work with a few files: They will be in the src folder. But mostly, we'll stay focused on App.js:

function App() {
  return (
    <div className="App">
      <h1>Notices</h1>
    </div>
  );
}

export default App;

Now let's customize our App.js to be for our app.

We'll render our different components inside our app:

import { useState, useEffect } from 'react';
import Aside from './components/Aside';
import Footer from './components/Footer';
import Header from './components/Header';
import Main from './components/Main';
import Nav from './components/Nav';

function App() {
  const [noticesState, setNoticesState] = useState({ notices: [] });
    return (
      <div className="App">
        <div className='container'>
          <Header />
          <Aside />
          <Main notices={noticesState.notices}/>
          <Nav />
          <Footer />
        </div>
      </div>
    );
}

export default App;

And that should do it!

We should see our Notices component render in the browser.

React Fetch

Let's make the AJAX request to our Rails server to get data. The data will be an index of all the notices.

Two things to keep in mind:

Make sure your Rails server is running.
The AJAX request below should not work. This is due to CORS, a basic security feature. We will talk about CORS specifically later.

NOTE: If you are getting a syntax error of < in JSON - try restarting your Create React app (control c then npm start again)

Make a request to the Rails server and console log the response.

function App() {
    const [noticesState, setNoticesState] = useState({ notices: [] });

     useEffect(() => {
          async function getNotices() {
            try {
              const notices = fetch('http://localhost:3000/notices')
              .then(response => response.json())
              console.log(notices)
            } catch (error) {
              console.log(error)
            }
          }
         getNotices();
     }, []);


    return (
      <div className="App">
        <div className="container">
          <Header />
          <Aside />
          <Main notices={noticesState.notices} />
          <Nav />
          <Footer />
        </div>
      </div>
    );
}


export default App;

If you get this:

screenshot

It means your Rails server is not running.

If you get a response like this, then you have the expected CORS issue:

screenshot

Otherwise, you should see your API data showing up in your browser console. This might happen if somehow your browser is ignoring the same-origin policy OR has localhost:3000 cached already.

Try emptying your cache and see what happens.

CORS

You should have received this error message when getting your react app on localhost:3001 to query your server on localhost:3000 :

screenshot

What's going on, here?

same-origin policy

Browsers implement a security feature called same-origin policy.

The idea is that Javascript requests to a server are rejected if they come from a different origin.

AJAX requests can't make requests to other servers than the one they're coming from.

TLDR: By default, AJAX requests must have the same origin and destination.

An origin is the combination of port, protocol and host.

To allow the browser to make a request to a different origin, we have to tell the server to accept cross-origin requests.

Cross-Origin Resource Sharing (CORS) is a technique for relaxing the same-origin policy, allowing Javascript on a web page to consume a REST API served from a different origin.

Understanding CORS

Any production API has to deal with the same-origin policy and enable CORS if a frontend server is to consume that API.

GOTCHA: You might run into CORS issues when you try to consume a third-party API.

Many projects have floundered because of third-party API CORS issues.

For this reason and others, we recommend hitting the third-party API from the backend if at all possible.

Configure Rails for CORS

Let's tell Rails to send through that Access-Control-Allow-Origin header that our browser is freakin' out about.

Uncomment the rack-cors gem in the Gemfile gem 'rack-cors' around line 28.

Gemfile:

# Use Rack CORS for handling Cross-Origin Resource Sharing (CORS), making cross-origin AJAX possible

gem 'rack-cors'

Make AJAX Request

In your frontend app, make the request to the backend app.

In Chrome and other browsers, the origin will be 'remembered' even if you change the CORS settings in the backend app. To reset, empty the browser's cache.

The request should work:

screenshot

The data will be in the data object (100 notices).

If killing and restarting Rails, and hard refreshing (cmd-shift-f) your browser did not resolve the CORS error, you might have to start your browser with same-origin policy disabled:

open -a Google\ Chrome --args --disable-web-security --user-data-dir

However, please let an instructor know if you have to run this, because it may hinder your progress during the next project week.

More Work With Our React Frontend

Let's format our data on our page

Display the AJAX'ed stuff

First, we need to add the notices we just pulled from our Rails API to this.state in App.js:

useEffect(() => {
    async function getNotices() {
      try {
        const notices = fetch('http://localhost:3000/notices')
        .then(response => response.json())
        setNoticesState({ notices });
      } catch (error) {
        console.log(error)
      }
    }
    getNotices();
}, []);

Once this is added, we should see the following in the browser:

screenshot

POST Request - Add a Notice to the Database

Before we begin adding our CREATE, UPDATE or DELETE functionality, we're going to modify the create, update & destroy actions inside of our rails API notices_controller file.

By default, create, update & destroy will only send back a copy of the model instance we're performing the service on. Unfortunately this make it more challenging to update state in React.

So, instead of sending back a single model instance for these actions, we'll send back the entire collection after all changes have been applied.

class NoticesController < ApplicationController
  before_action :set_notice, only: [:show, :update, :destroy]

  # GET /notices
  def index
    render json: get_notices # 👈 send back all the notices
  end

  # GET /notices/1
  def show
    render json: @notice
  end

  # POST /notices
  def create
    @notice = Notice.new(notice_params)

    if @notice.save
      # send back all the notices
      #               👇
      render json: get_notices, status: :created, location: @notice
    else
      render json: @notice.errors, status: :unprocessable_entity
    end
  end

  # PATCH/PUT /notices/1
  def update
    if @notice.update(notice_params)
      render json: get_notices # 👈 send back all the notices
    else
      render json: @notice.errors, status: :unprocessable_entity
    end
  end

  # DELETE /notices/1
  def destroy
    @notice.destroy
    render json: get_notices # 👈 send back all the notices
  end

  private
    # private controller class method we can reuse inside of index, create, update & destroy.
    
    # This will allow us to render our entire collection of notices as a response.
    
    # so we can up our component state in react with a fresh array
    def get_notices
      Notice.order('created_at DESC')
    end

    # Use callbacks to share common setup or constraints between actions.
    def set_notice
      @notice = Notice.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def notice_params
      params.require(:notice).permit(:title, :author, :phone)
    end
end

Now that we've taken care of that, in order to create a notice, we will need to get our formInputs from the Form component. We will do this in a handleAdd function that sends that form data to the Rails API.

function App() {
  const [noticesState, setNoticesState ] = useState({ notices: []});

  useEffect(() => {
      async function getNotices() {
        try {
          const notices = fetch('http://localhost:3000/notices')
          .then(response => response.json())
          setNoticesState({ notices });
        } catch (error) {
          console.log(error)
        }
      }
      getNotices();
  }, []);
  
  async function handleAdd(formInputs) {
      try {
        const notices = await fetch('http://localhost:3000/notices', {
          method: 'POST',
          headers: {
            'Content-Type': 'Application/json'
          },
          body: JSON.stringify(formInputs)
        }).then(res => res.json())

        setNoticesState({ notices });
        
      } catch(error) {
        console.log(error)
      }
    }
  //... and pass this into the Aside

  <Aside handleAdd={handleAdd} />
}

We won't need to do any further "prop-drilling" to connect the handleAdd function to the Form component as this has been taken care of for us in the starter code.

Delete

Since our data is rendered all the way down in the Notice component but state is all the way up in the App, we should build out the functionality of delete up in app and pass down the functionality.

App.js

  function handleDelete(noticeId) {
    try {
      const notices = await fetch(`http://localhost:3000/notices/${noticeId}`, {
        method: 'DELETE',
      }).then(res => res.json());
    
    setNoticesState({ notices });

    } catch (error) {
      console.log(error)
    }
  }

Pass it down

<Main
  notices={noticesState.notices}
  handleDelete={handleDelete}
/>

Pass it down Main.js

function Main({ notices, handleDelete }) {
    return (
      <main>
        <Notices
          notices={notices}
          handleDelete={handleDelete}
        />
      </main>
    );
}

Pass it down

Notices.js

function Notices({ notices, handleDelete }) {
    return (
      <div>
        {notices.map(notice => 
          <Notice 
            key={notice.id} 
            notice={notice}
            handleDelete={handleDelete}
        />)}
      </div>
    );
}

Notice.js

function Notice(props) {
    return (
      <div className="notice">
         <h3>{props.notice.title}</h3>
         <p>{props.notice.author}</p>
         <small>{props.notice.phone}</small>
         <button onClick={()=> props.handleDelete(props.notice.id)}>X</button>
       </div>
    );
}

Update

Here is the strategy for our Update functionality:

Replace card with a form by clicking an edit button.
Replace form with card also on button click.

Where does state for all of this go?

The data for notice belongs all the way in app since we're making our AJAX requests and updating that state there.

We'll also need a new piece of state for showing or hiding an edit form inside the Notice component.

Let's start with the Notice component.

Let's import useState from react and initialize it as editFormVisible state set to false.

import { useState } from 'react';

function Notice(props) {

  const [editFormVisible, setEditFormVisible ] = useState(false);

  return (
    <div className="notice">
       <h3>{props.notice.title}</h3>
       <p>{props.notice.author}</p>
       <small>{props.notice.phone}</small>
       <button onClick={()=> props.handleDelete(props.notice)}>X</button>
     </div>
  );
}

export default Notice;

... then we import our Form component

import Form from './Form.js';

Let's write a function that once invoked, will toggle our form

function toggleForm() {
  setEditFormVisible(!editFormVisible)
}

  return (
    // ... more code below

Add a ternary operator to change our view based on state and a button with an event prop for toggling the form

  function toggleForm() {
    setEditFormVisible(!editFormVisible)
  } 

  return (
    <> 
      { editFormVisible ?
        <Form />
        :
        <div className="notice">
          <h3>{props.notice.title}</h3>
          <p>{props.notice.author}</p>
          <small>{props.notice.phone}</small>
          <button onClick={()=> props.handleDelete(props.notice)}>X</button>
          <button onClick={toggleForm}>Edit</button>
        </div>
      }
    </>
  );

Let's pass down our notice & toggleForm into our Form

<Form 
  notice={props.notice}
  toggleForm={toggleForm}
/>

Let's write some logic that if there are props, we'll populate the form with the notice to edit.

Form.js

We'll also need to grab the id for our route, even though it never goes in as part of an input field.

We'll use the useEffect hook to check for the notice prop and then use that information to populate our form if needed

don't forget to import it into Form.js

  useEffect(() => {
    if(props.notice) {
      const { title, author, phone, id } = props.notice;
      setFormState({
        title,
        author,
        phone,
        id
      })
    }
  }, [props.notice]);

Let's write our update function and send it down

App.js

async function handleUpdate(formInputs) {
  event.preventDefault();
  try {
    /* 
      we'll destructure the formInputs values so we can seperate the id,
      and use it for the url param. We don't want to send the id to the server
      as it's not included in our rails controller permit params
    */
    const { title, author, phone, id } = formInputs;
    const notices = await fetch(`http://localhost:3000/notices/${id}`, {
      method: 'PUT',
      headers: {
      'Content-Type': 'Application/json'
      },
      body: JSON.stringify({ title, author, phone }),
    }).then(res => res.json())
    setNoticesState({ notices })
  } catch (error) {
    console.log(error)
  }

Then send it down:

App.js

<Main
  notices={state.notices}
  handleDelete={handleDelete}
  handleUpdate={handleUpdate}
/>

And down:

Main.js

import Notices from './Notices.js';

function Main({ notices, handleDelete, handleUpdate }) {
    return (
      <main>
        <Notices 
          notices={notices} 
          handleDelete={handleDelete}
          handleUpdate={handleUpdate}
        />
      </main>
    );
}

export default Main;

And down:

Notices.js

import Notice from './Notice.js';

function Notices({ notices, handleDelete, handleUpdate }) {
    return (
      <div>
        {notices.map(notice => 
          <Notice 
            key={notice.id} 
            notice={notice}
            handleDelete={handleDelete}
            handleUpdate={handleUpdate}
          />
        )}
      </div>
    );
}

export default Notices;

And down:

Notice.js

return(
  <>
  { editFormVisible
     ? <Form 
          notice={props.notice}
          toggleForm={toggleForm} 
          handleUpdate={handleUpdate} 
        />

There are a few more things we need to add in Notice.js to tie our update together:

We need to run toggleForm when we click an "Edit" button
We need to run toggleForm plus props.handleUpdate upon submit of the form

Form.js

  function handleSubmit(event) {
    event.preventDefault();
    if (props.notice) {
      props.handleUpdate(formState)
    } else {
      props.handleSubmit(formState);
    }
  }

We also need to update the button text based on whether we are updating an existing notice or adding a new one:

Form.js

   <input type="submit" value={props.notice ? "update this notice" : "add a notice"}/>

We Did It!

Now we have a reference application that demonstrates how to consume JSON data with React from a Rails backend.