Clojurians Log v2

How often, if ever, would you make a nested comp/get-query call?

@tony.kay Hello! I went on a walk this evening and I was pondering about Fulcro. I got reminded that when I first started playing with Fulcro I found the idea of normalising data via component queries neat, and it made perfect sense for examples I could come up with (e.g. a Todo component mapping to a Todo entity, etc), but it wasn’t obvious to me (and still isn’t) that the model generalised (e.g. that I wouldn’t have a component corresponding to two distinct data nodes, etc). Have you found this to be a limitation or a problem in practice?

Could you clarify? Are you saying that if you have some {:todo/id 1 :todo/title "..."} on the screen you wouldn't expect fulcro to be capable of drawing it on the screen twice?

@hmaurer no. The model generalizes in the following ways: • Two different things that need to display in a hetero list (e.g. a timeline feed with news/images/etc): Union queries • A component that has a mix of data from various places in the real back-end db: Keywords are namespaced. Query resolution can combine disparate things into a view, and save logic can pick them back apart. Anything that can displayed this way must by its very nature be to-one in relation (otherwise you’d have to have an edge to traverse, which would lead to children with different IDs). Thus, merging data implies that you can “merge IDs”…e.g. :account/id and :primary-address/id can co-exist in a single component even though more than on ID corresponds to elements on that UI. Save, of course, has to know that fields need what IDs. RAD solves that by having you declare what identities (a keyworkd like :account/id) identifies the entity(ies) on which that fact can be saved or read.

@tony.kay thanks for writing this up. Follow-up question, then: how would you deal with, say, a “CompareVehicles” component which lets you pick two vehicles (entities in the DB) and compare them (imagine a side-by-side table).

a container with either a single to-many join (with 2 elements) or two edges that I made up :left-car :right-car

[{:left-car (comp/get-query Car)} {:right-car (comp/get-query Car)}]

or [{:cars-to-compare (comp/get-query Car)}]

the latter supports n-compare screen

I am getting following message twice (same Router) on startup since I updated to 3.2.16:

WARN [com.fulcrologic.fulcro.ui-state-machines:215] -  #error {:message "", :data {}} Attempt to get an ASM path [:com.fulcrologic.fulcro.ui-state-machines/local-storage :path-segment] for a state machine that is not in Fulcro state. ASM ID:  :decide.ui.root/PageRouter

“breaks” or gives warning?

There is sort of a race condition between initial state (which has no state machines in it) and any attempt to find the “current route”. That is what initialize! is about: it tries to make sure the machines are started. Ideally, the real initialization is to do a sequence like this:

(app/set-root! SPA Root {:initialize-state? true})
(dr/initialize! SPA)
(app/mount! SPA Root "app" {:initialize-state? false})

that will prevent the UI from looking for the current route before there is one…ideally you’d also change-route! before the mount as well

I need to update the book…it is possible my recent cleanups show more warnings than before, but should not have “broken” anything

Could someone give me a quick sanity check?: I've roughly the following attributes/entities:

(defattr category-id :category/id :uuid {ao/identitiy? true})
(defattr element-id :element/id :uuid {ao/identity? true})

(defattr content-id :content/id :uuid {ao/identity? true ao/identities #{:category/id :element/id})

In .16 i just got the message from above. In .17 it is followed by a lot of red on my console something about deref of nil in current-route. No render anymore. I am currently not on my computer. I will look for details tomorrow.