Adding guestbook-datomic

[Folcon]

Issue to coordinate adding a guestbook-datomic example.

The template for this example was created with the flags below.

lein new luminus guestbook-datomic +datomic +re-frame

The code is at https://github.com/folcon/examples.

[Folcon]

One thing that might be useful to add to the template in dev-config.edn is this message:

; Don't forget you can also use the datomic mem db which can be useful when developing
; :database-url "datomic:mem://guestbook_datomic_dev"

Not sure how you template the project name.

[yogthos]

ah good call on adding a comment, I'll take a look

[Folcon]

So I'm getting a fun problem. My datomic keys are being converted to json incorrectly I believe? My code feeds the result straight to the response function:

(response/ok (db/get-messages db/conn))

So for example, a message list such as:

[{:db/id 17592186045418 :message/id #uuid "bc7024b1-c8c0-4c8d-b7d1-a7d9e5044ad0" :message/name "Test name" :message/message "Test message"}]

is converted to:

[{":db/id":17592186045418,":message/id":"bc7024b1-c8c0-4c8d-b7d1-a7d9e5044ad0",":message/name":"Test name",":message/message":"Test message"}]

Which then is read out as:

{::db/id 17592186045418, ::message/id "bc7024b1-c8c0-4c8d-b7d1-a7d9e5044ad0", ::message/name "Test name", ::message/message "Test message"}

I was expecting it to convert to json automatically. Am I calling this incorrectly?

[Folcon]

@yogthos Other than the above issue, I've got it mostly working. Would like to get this wrapped up today if possible.

[yogthos]

:+1:

[yogthos]

Regarding the JSON conversion, you probably would want to use transit between the client and the server. As I recall the middleware uses the accept header to infer what format things should get serialized in. As I recall cljs-ajax should be defaulting to transit though.

[Folcon]

Hmm, it doesn't seem to be working well. In both cases I get message keys like:

":db/id", ":message/id", ":message/name"

Which get converted to:

::db/id, ::message/id, ::message/name

The same as when I do:

(keyword ":message/name")
;=> ::message/name

Whereas I want:

(keyword "message/name")
;=> :message/name

Because

encoding(input) => output
decoding(output) => input

right?

Perhaps I should be converting the output of the datomic db? Which currently gives:

[{:db/id 17592186045418 :message/id #uuid "bc7024b1-c8c0-4c8d-b7d1-a7d9e5044ad0" :message/name "Test name" :message/message "Test message"}]

transmit+json gives:

[["^ ",":db/id",17592186045418,":message/id","~u016b7492-0e35-45d5-afea-f0ac31ba38af",":message/name","Test message",":message/message","Test message",":message/timestamp","~m1528575843965"]]

Also I could push what I currently have if you're puzzled about the issue I'm coming across?

[Folcon]

Ok @yogthos, worked out the issue. Had done the pull syntax incorrectly. I didn't realise you could get it to wrap elements in strings. More flexible than I expected.

I've pushed an update, give it a look when you have some time and tell me if you want me to make some updates to it!

[yogthos]

Thanks, I'll try take a look shortly. I think you should be able to send Datomic results directly to the client as long as they're in EDN format. Once transit+json is deserialized, it should look like the original data on the other end.

[rberger]

Is there a tutorial to go along with guestbook-datomic? Though what I'm really looking for is a tutorial for using re-frame with Luminus. This is the closest I could find.

[yogthos]

There isn't a tutorial to go along with the sample project at the moment. This re-frame workshop might be helpful though. Luminus just sets up the basic scaffolding for re-frame, so how you structure the app beyond that is mostly up to you.

[Folcon]

@rberger What kinds of things would you like to see in a tutorial? I've been using datomic more and more in my reframe app, so happy to try and document things and put it back into tutorial form =)... Also @yogthos, sorry about not getting back in touch sooner, if you have improvements you'd like me to make to what I've documented, could spend some more time on that.

[yogthos]

@Folcon if you have a chance I'd suggest adding a small walkthrough in the readme for the guestbook-datomic project. Alternatively, you could add a Datomic section in the database doc page. I'd focus on Luminus specific aspects of getting Datomic up and running, and refer to the official docs for further details.

[Folcon]

Gah, sorry @yogthos, I keep meaning to respond when I have something and unfortunately at the moment most of my focus is on the frontend side of development. However the datomic code I have working is in production, so there's little chance of me not doing this, if only to ensure I document it for myself to read in the future ;)...

It's just that I doubt I'll be going anywhere near it until at least January. My plan is to document useful stuff as I go when I next touch it so the intent is to put that here then.

[yogthos]

No rush, it's going to be pretty great to have docs based on actual real world experience though. :) I'm also open to improving the Datomic profile to make things smoother if you have any ideas there.