strange…not sure how that happened

that's a really good talk!

Well I just fought this issue for the last 5 hours and finally figured it out just this second. Let's take the RAD demo as basis: https://github.com/fulcrologic/fulcro-rad-demo/blob/master/src/shared/com/example/ui.cljc I have a component AnotherRoot in another namespace. This component has a nested, dynamic router. I have that router composed into AnotherRoot via :pre-merge as described in the docs. Then I added AnotherRoot to the MainRouters :Router-targets of the demo. I assumed this should be enough, since the MainRouter gets composed into the Root component, but apparently I was wrong. The nested router did work for simple routes without arguments, but throws an error for routes with arguments. What finally resolved it was also adding AnotherRouter to Root :query

Here's the code I'm describing: https://gist.github.com/Xceno/db47160674f4b2832479d700dee244e7

what a coincidence! I'm trying to understand what's happening here, I assume the part you're referring to in the book is http://book.fulcrologic.com/#_initial_state_2 right?

reading your code now... in my case I have RootRouter pointing to NestedRouter , and a FooComponent which isn't getting its initial state in props

I don't have pre-merge on any of them, didn't realize it was necessary

hm ok looks like my problem wasn't router related at all... so I have this component, for some reason it wasn't getting props with its initial state in it:

(defsc ProjectSettings [this {:project/keys [id name] :keys [active-tab] :as props}]
  {:query         [:project/id :project/name :active-tab]
   :ident         :project/id
   :initial-state {:active-tab "0"}
   :route-segment (r/last-route-segment :project-settings)
   :will-enter    (fn [app {:keys [id]}]
                    (dr/route-deferred
                      [:project/id (uuid id)]
                      #(df/load! app [:project/id (uuid id)] ProjectSettings
                                 {:post-mutation        `dr/target-ready
                                  :post-mutation-params {:target [:project/id (uuid id)]}})))}

:pre-merge     (fn [{:keys [data-tree] :as m}]
                    (merge (comp/get-initial-state ProjectSettings)
                           (fm/sweep data-tree)))

Pre-merge is part of the dynamic story….the fact that you’re loading the target is the issue. initial-state has nothing to do with loads…it is for the very first frame (instant) of your application’s lifetime. From there it has nothing to do with anything unless you explicitly call it. It’s called initial-state, but should probably have been called state-used-for-application-startup-only or something 🙂

Something has to make the initial database of your app (which is in the state-atom and is commonly referred to as the application state)…thus the name.

it has nothing to do with the initial state of anything else…if you loaded something, then obviously the data you loaded is the state of the thing, not the initial state.

thanks @tony.kay, i got it now--I think the problem in my intuition was that I was expecting the load to merge the new data with the old data rather than replace the old data. Nothing a pre-merge can't fix though

@U49U72C4V if you can think of better wording / further clarification for the relevant parts of the Book, please send a PR!

can't immediately think of what gave me this impression--maybe a warning box in one of the load sections or the dynamic routing section saying something like "hey if you had any other data on this ident it's gonna disappear after a load". i'll submit a PR if a good idea comes to me 🙂

> if you can think of better wording / further clarification for the relevant parts of the Book, please send a PR! I'm currently collecting all kinds of notes about fulcro, specifically "how to" examples and typical errors i run into while learning it on the go. Once I built up my collection I'll clean in up and translate it. I hope there's some stuff I can contribute back