Ep 021: Mutate the Internet

Functional Design in Clojure

Nate wants to tweet regularly, so he asks Clojure for some help.

• Problem: pre-author tweets so they can get posted automatically.
• Want to make a "full stack" application this time.
• Sounds complicated, what do we need?
  • Database of tweets: text to tweet and timestamp when it should be tweeted.
  • Frontend is a single-page application (SPA) that makes XHR ("AJAX") requests to the backend.
  • Needs to be able to wake up and post.
  • Persistent process backend.
• We will not cover all these parts.
• "You have a problem, so you make a UI to solve your problem. Now you have 2 problems." "More like 18 problems!"
• We will focus on logic interacting with Twitter.
  • When should it post?
  • How does it know if a tweet has been posted?
  • What to do when Twitter returns an error?
• Overarching theme: how do you deal with side-effects in a functional way?
• Remember Ep 020: push side-effects and I/O to the edges.
• Easy to fetch "current" time, but that's a side effect!
• "Just because it's easy doesn't mean it's pure."
• If you make time a parameter, all of a sudden you can mess with it!
• "If only real time was a parameter we could manipulate."
• Lots of fun to be had in the upcoming episodes.
• "'Start with the data' is something we've come to again and again. If you can model the data, that's a very good place to start."

Related episodes:

• 006: All Wrapped Up in Twitter
• 020: Data Dessert

Related projects:

• Maria

Clojure in this episode:

• nil