1702 Express/Sequelize/Associations Review

Quick review session for 1702 FSA/GH students for Express and Sequelize and Sequelize association methods

To view the express only version of this repo, check out this branch

To view the express-sequelize version of this repo, check out this branch

Videos

Playlist for the video review of this repo being built can be found here

Individual Videos:

Sequelize Part 1 - basic structure Part 2 - associations

NB: This was all live review, there may be some small inaccuracies in how things are described but I tried to repeat most of the questions for viewers

Starting up

To start up:

createdb puppies in the command line to create your postgres database
npm install to install node modules
npm run seed to seed your DB with the latest and greatest puppies/parks/locations/etc (this will clear/reset the db)
npm run seed:associations to seed some semi-randomized associations in your puppy instances
or
npm run seed:all to seed the instances and also the associations
npm start starts the server, you can now make requests to localhost:3000

Routes to try:

The server will start listening on localhost:3000 by default

Fire up an easy http client like Postman and try some routes like:

GET: /puppies
POST: /puppies
GET: /puppies/:id

Check out all the routers in /routes for more options!

Part 1: Express

Express Review questions

Dealing with queries and how to route them?

Dealing with multiple :params in the URI? How to make sure the right route?

What is static middleware???

Express routing:

Express is basically a big nested queue. Express goes through middleware and attempts to match the request path to middleware. If it matches an app.use sub-router on the way, it enters that sub-router and attemps to match against its

try {
// JS array notation is just shown here as a demo of the queue structure - express iterates through this and tries to match
[
  //matches this route
  app.use,
  //matches this route
  app.use,
  //if the path matches this /path, ener the router within which is another queue
  app.use('/path' [app.get, app.post]),
  // if the path matches this /path, enter
  app.use('/path2'),
  // match all paths and handle errors callback with 4 arguments
  app.use('*', function(4 arguments),
  // defaults to sending a 404 if no routes match
  app.use('*', function(req, res, next){ res.sendStatus(404)})
]
// if errors are caught, express helps handle
} catch(error) {
  res.status(500).send(error) // internal server error
}

Netflix and Express:

Cool article on Netflix using express servers and running into erro http://techblog.netflix.com/2014/11/nodejs-in-flames.html

Part 2: Sequelize

Questions:

Remind us which aspects are coming from Sequelize vs Express - where's the logic living? Where do I look in the docs - express or sequelize?
- General answer: anything dealing with req or res is in express docs. Anything in a Sequelize promise chain that's not touching either req or res - look to the Sequelize Docs
Sequelize methods - what do we get and how do we use them?

Important Methods:

Model.findAll() finds all instances
Model.findAll({where: {.......}}) finds all instances that match the where condition
Model.findOne({where: {....}}) finds first match for the where condition
Model.findById(id) finds by an id number. Sequelize will coerce strings into ints, so you can simply use the req.params.id and not worry about casting to a Number before sending to Sequelize
Model.findOrCreate({where: {.....}}) will find an entry OR create it if necessary. returns Instance as first argument, and created boolean as the second. Good for making sure you don't make a bunch of duplicates
if the above queries return nothing, return value will be null

Part 3: Sequelize Association Methods:

For this segment of the review, we significantly changed the starting point from the previous ending point in order to save time during the live review. 3 new models were defined: Park, Location, and Food, with corresponding basic routers. The file structure was expanded so that there are separate /routes and /models folders. Seed data was also added in the seed.js and seedAssociations.js

This document explains more about the Sequelize methods and a bit more about what we aimed to do with this review session

You'll notice some new seeding files in this branch - this is to illustrate a bit about how to construct seed files, with or without associations