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:

Express: Part 1 Part 2

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