This is a really simple demo of working with a python + flask backend and a clojurescript + reagent frontend, with a figwheel workflow.

It appears that you can use flask with figwheel without much problem using off-the-shelf workflows, if you're willing to accept some "extra" stuff that figwheel is doing...

It's best to start figwheel first, since the python server isn't going to work at all until you've got compiled javascript, which is one of the things figwheel takes care of. So run

lein fighweel

from the project root.

When you run this, all your clojurescript gets compiled. Furthermore, figwheel

• starts a dummy server on 3449 to serve up your index and other assets
• starts a websockets connection that browsers will connect to for a clojurescript repl

Once figwheel is ready, it will pop open a browser window on port 3449.

You'll notice that the heading which we expected to change to say hello from flask doesn't change; if you open the dev console, you'll see a 404 error when it tries to hit the /newtext endpoint. This is because the figwheel asset server doesn't have any json endpoints.

In a new terminal, run

python app/server.py

You'll see all the usual flask logging from your backend.

This app, importantly, knows to serve any path that doesn't match some other route by looking in ../resources/public, relative to the server.py file. Without this, the css and all of the javascript loads would fail.

Go to localhost:5000 in the browser.

This time, you should see the hello from flask message come up, which is how we know that the flask backend is working properly.

If you make some edits to clojurescript and save them (make a syntax error, it's more fun that way), you'll see that the figwheel auto-compile and auto-reload is working as it should.

How did this work? We just stood up two different backend servers, one on 5000 and one on 3449, and connected two browser windows to them. But fighweel seemed to connect to both of them just fine.

What it actually appears to be doing is broadcasting reloads and also repl commands to all clients. You can test this in very rough terms by running - with both clients connected - (js/alert "hi"). You'll probaly get an alert popping up in both browser windows.

To start off with a figwheel + reagent template, I just ran lein new fighweel pycljs -- --reagent. Then, I made an app folder for my python backend and copied in some boilderplate from a previous flask app I'd written.

I haven't tried it yet, but I think to get a release going, all you need to do in theory is lein do clean, cljsbuild once min.

Copyright © 2016 Steven Troxler

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.