Compojure and Integrant
Recently I’ve been playing around with some compojure-api stuff for some side projects and alphas and decided somewhat foolhardily to try moving away from Mount as my component management tool. I like Mount; despite some drawbacks of the pattern, modelling databases as singletons clicks with me logically and as I don’t tend to run tests from the repl, I’ve not had the same pain points around testing and reloading that many have had with it.
Anyway, integrating Integrant was a bit of a pain, but here’s how you do it:
- You make sure that your databases are modelled as components
- Any components that need access to the database reference your database component
- That dependency is then injected and can be accessed by code in that closure
- Repeat for all your components
NB: it’s worth saying at this stage that choosing Duct as your web toolkit and using integrant-repl will allow you to adopt a reloaded-style workflow more easily than integrating with an existing project.
You can see that this is a pretty different pattern from just dereferencing a var, and we’ll see how you can set that it up to work in that way in development in just a sec.
So, for a simple compojure-api project with just a web stack and database, we might have the following config file:
We then write initializers for Integrant so it can make components out of our connections and depedencies. To componentize our web stack, we simply wrap the def in a closure and make it a defn.
Finally, if you want to manually be able to reference your system and start and stop it in development, you can use something like the below, although checking out integrant-repl is probably the best call.
I’ll hopefully do a post soon on how to prep this for production use.
Update: I’ve added some notes on getting integrant-repl set up for dev here.
Alex Lynham
Notes on working for a startup in Manchester and various other projects.
alex@lynh.am
