9. Your First Fullstack App!

Follow along with code examples here!

Remember, the model is the layer of the application that directly manipulates the data. It provides methods that the controllers can use to execute those changes whenever the frontend makes the appropriate request.

Thus far, our server application used an in-memory array as a "database". But this data is not persistent — each time we restart the server, all data created during that running session is lost.

Now that we have a database and can connect to it using Knex, we can refactor our model to use that database and have our data persist.

Part 1 - Adding a DB for the fellows

Open the repository and start with the 2-fellow-tracker-final-mvc/ version of the project.

We need to create a database and then replace all logic associated with the in-memory fellows array used in the server/model/Fellow file with knex code to connect with our new database.

1. Start your Postgres server and create a database called fellows_tracker using TablePlus or the psql CLI.

2. Execute the SQL statement below to create the table structure

   CREATE TABLE fellows (
     id SERIAL PRIMARY KEY,
     name TEXT NOT NULL
   )

3. Return to the repository and install pg and knex into the server directory. Then initialize knexfile.js:

   cd server
   npm i pg knex # install pg and knex
   npx knex init # create knexfile.js

4. Modify knexfile.js to use pg and the fellow-tracker database with a valid username and password:

   development: {
     client: 'pg',
     connection: {
       user: 'postgres',
       password: 'postgres',
       database: 'fellow-tracker', 
     }
   },

5. Create a knex.js file in the model/ directory that exports a knex object. Remember, this object will be shared by every model in our application to execute SQL statements to the database.

   • make sure the import statement for knexfile.js is accurate

   // Set the deployment environment variable
   // Depending on where it is deployed, this could be "staging" or "production"
   const env = process.env.NODE_ENV || 'development';
   
   // Grab the corresponding knex configuration object from knexfile.js
   const knexConfig = require('../knexfile.js')[env];
   
   // Create the knex connection object using that config
   const knex = require('knex')(knexConfig);
   
   module.exports = knex;

Part 2 — Refactor!

Knex is configured to connect to our database! Now we can execute SQL commands to the database using the knex.raw() method.

Head over to the server/model/Fellow.js file and remove all logic associated with the in-memory fellows array, replacing it with the appropriate knex and SQL logic.

Remember, knex.raw() returns a promise that resolves to an object with a rows array property, even if there is only one value returned by the query!

const getPets = async () => {
  // knex.raw returns a query result object
  let result = await knex.raw("SELECT * FROM pets");
  
  // .rows is an array containing the query data
  return result.rows;
};

Here's what you need to do:

1. Import knex into the Fellow model

2. Remove the import of the getId function, the database will handle automatically setting the id property

3. Remove the fellows array

4. All methods need to be async to use await knex.raw()

5. Every function needs to return something (use RETURNING * on all non-SELECT queries)

   1. Fellow.create should return the new fellow

   2. Fellow.list should return an array of all fellows

   3. Fellow.find should return a single fellow object (the first object in the rows array)

   4. Fellow.editName should return the updated fellow object

   5. Fellow.delete should return the deleted fellow object

6. Refactor fellowControllers.js to await everything and double check that all values returned from the model are being handled properly.

Part 3 - Adding posts

Here's where things get fun! We can add a posts table to our database that has a one-to-many relationship with our fellows table. Each post must have a fellow_id reference pointing to the fellow that created it.

1. Create a posts table that references the fellows table

2. Create a Post model with methods:

   • create(content, fellowId)

   • findPostsByFellowId(fellowId)

   • delete(id)

   • deleteAllPostsForFellow(fellowId)

   • list() — only used for testing

   • findById(id) — only used for testing

3. Make the postControllers

4. Define endpoints in index.js. Make sure to follow REST principles! Since every post is owned by a fellow, the endpoint should communicate that:

   • POST /api/fellows/:fellowId/posts → Post.create

   • GET /api/fellows/:fellowId/posts → Post.findPostsByFellowId

   • DELETE /api/fellows/:fellowId/posts/:postId → Post.delete

   • DELETE /api/fellows/:fellowId/posts/ → Post.deleteAllPostsForFellow

5. Test with postman

6. Add frontend components and fetching on the FellowDetails page

   • You'll need the following components:

     • A form for adding a new post

     • A list of posts with delete buttons for each post

   • Event handlers / fetching:

     • useEffect now also fetches fellow posts -> GET /api/fellows/:fellowId/posts

     • new post form on submit -> POST /api/fellows/:fellowId/posts/

     • list item delete button on click -> DELETE /api/posts/:id

7. When deleting a fellow, we need to delete posts first. How can we ensure that this happens in the right order?