Clojurians Log v2

hi everyone

any ideas what does this mean? mount.core.DerefableState cannot be cast to com.mongodb.DB

I create a project using lein new luminus my-app +re-frame +mongodb

which generates my_app.db.core file, that has the following function

(defn create-user [user]
  (mc/insert db "users" user))

and if I call this function from my routes/home.clj file, I get that error basically

That means you’re using mount to manage your connection to the database, and it hasn’t connected to the database yet.

could it be a credentials error?

or is it just taking time?

Could be either one. I’d try playing with it at the repl and see if it’s throwing any errors and/or returning a value for db eventually.

Also be sure mount/start has finished before running the create-user fn.

is there a way to make sure it has finished ? 😄

Actually, that’s probably a bad way to phrase it. I should have said make sure your code is calling mount/start before the call to create-user — if they’re both in the same thread, then you should be good

ah right. yeah I think they are, so probably it’s something to do with credentials.. I’ll see if I can connect to repl somehow

throws the same exact error in repl 😞

I’m using your lein new command to create my own copy of my-app and see if I can see anything useful — have you made many change to the project yet, other than the mongo credentials?

nope, nothing at all

ok, good, I should be seeing the same code you are then

I’ve just created a new function under db/core.clj

(defn get-users []
  (mc/find-maps db "users"))

and it throws the same error

What’s your working environment? Emacs? Atom? Cursive?

emacs

well, spacemacs

jack-in doesn’t work unfortunately

Ok cool. My spacemacs is getting a bit rusty, but I can suggest some things

yeah sure

Try shutting everything down and then do

$ lein repl
> (in-ns 'my-app.core)
> (start-app)

That should give you some output about mount starting things up

👍 I’ll give it a shot now

then maybe (clojure.pprint/pprint my-app.db.core/db) and see if you have a db connection or a mount/DerefableState

it is a DB connection

Ok, so it sounds like start-app isn’t getting called. How are you starting the app?

lein run and then lein figwheel

and I haven’t changed any defaults

Hmm, ok, lein run should be calling start-app — do you have an environment variable named DATABASE_URL?

ok I think it works now

I’ll just restart the app once more and test

re: your question, I don’t have a variable with that name. but I think for some odd reason, it works now..

Maybe it just needed a bit of extra time to start up before you call lein figwheel

Here’s what I get when I start it up:

env DATABASE_URL="<mongodb://localhost/my-app>" lein run
2019-01-21 10:47:04,271 [main] DEBUG org.jboss.logging - Logging Provider: org.jboss.logging.Slf4jLoggerProvider
2019-01-21 10:47:04,643 [main] INFO  my-app.env -
-=[my-app started successfully using the development profile]=-
2019-01-21 10:47:04,768 [main] INFO  luminus.http-server - starting HTTP server on port 3000
2019-01-21 10:47:04,814 [main] DEBUG io.undertow - starting undertow server io.undertow.Undertow@2223232e
2019-01-21 10:47:04,824 [main] INFO  org.xnio - XNIO version 3.3.6.Final
2019-01-21 10:47:04,932 [main] DEBUG io.undertow - Configuring listener with protocol HTTP for interface 0.0.0.0 and port 3000
2019-01-21 10:47:04,986 [main] INFO  org.projectodd.wunderboss.web.Web - Registered web context /
2019-01-21 10:47:04,988 [main] INFO  my-app.nrepl - starting nREPL server on port 7000
2019-01-21 10:47:05,007 [main] INFO  my-app.core - #'my-app.config/env started
2019-01-21 10:47:05,007 [main] INFO  my-app.core - #'my-app.handler/init-app started
2019-01-21 10:47:05,007 [main] INFO  my-app.core - #'my-app.handler/app started
2019-01-21 10:47:05,007 [main] INFO  my-app.core - #'my-app.core/http-server started
2019-01-21 10:47:05,007 [main] INFO  my-app.core - #'my-app.core/repl-server started

yep, the same here. I wasn’t getting that before though

so yeah it could be that it was taking time

thank you very much 🙂

I appreciate your help

Ok, cool, I’d say do lein run, wait for that stuff to print, then lein figwheel, should be reliable.

:thumbsup:

how did you call the fn inside db/core.clj from routes/home.clj?

I required it like so

[my-app.db.core :as db]

and then

(defn home-page []
  (let [users (db/get-all-users)]
    (layout/render "home.html" {:users users})))

and in my home.html I was doing

{{ users }} and {{ users|count }}

what's the original code generated by the template like?

original one just didn’t have that function, but even if I used the one in the original:

(defn get-user [id]
  (mc/find-one-as-map db "users" {:_id id}))

it was still throwing the same error

in fact, when you called the db.core/some_fn in routes.home ns, the error was thrown

without the calling, even if you add some fns into db.core ns, no error will be thrown

I think some_fn of db.core ns must have be called before the mount/start fn family called

maybe, but then i’m not sure how that would happen, as routes.home is started from start-app function and only then should it have called the db.core function

ok another question.. loads of frameworks like Laravel (PHP) or Buffalo (Golang) come with tools like artisan and grifts respectively, that run command line commands. for example php artisan db:seed will seed the database and then you can add as many command line functions as you want. so I want to add something similar to my luminus app. but I can’t figure out how would I do it, since lein run will always call the main function. Is there a way to somehow map some custom functions to lein scripts / commands? like for example if I run lein seed to call my-app.db.seeds/database-seeder function?

that's plugin

if you use a plugin lein-seed, you could use the command lein seed