Ian's NativeStore looks an interesting approach to the problem. There's also some new work in progress in master, the examples `two-lists` and `refs` if you are willing to spend some time reading uncommented code. Lengthier explanations are planned.
David On Sun, Oct 5, 2014 at 5:23 AM, Viksit Gaur <[email protected]> wrote: > Hello all, > > Any updates on this issue in terms of - how do I access different parts of > the app state from different locations? > > Thanks! > > On Wednesday, April 9, 2014 3:33:31 AM UTC-7, Daniel Kersten wrote: >> Hi, >> >> >> I'm trying to figure out the best way of structuring complex applications in >> Om and I've hit a bit of a brick wall that I'm hoping someone can help me >> with. >> >> >> >> >> I like the concept of cursors - narrow down the application state to what >> the individual components actually need and allow them to read and modify >> only that. >> >> >> The problem I'm having is that I don't know how to structure my state so >> that the correct components have access to everything they need. Its easy if >> each component only requires a strict subset of its parent, which is often >> the case, but not always. I've hit a scenario where a component needs access >> to two very different branches of the app state and I'm not sure how to pass >> it to the component that needs it. >> >> >> >> >> As a (contrived) example, imagine you had an app for displaying orders in an >> online store and the application state is something like this: >> >> >> (def app-state (atom {:items [{:type "book" :price 123} {:type "cd" :price >> 200}] >> >> >> :orders [{:date xxx :type "book" :count 3} {:date yyy >> :type "cd" :count 1}] >> :filter "book"})) >> >> >> >> >> You can imagine that in a real application the :items and :orders branches >> may be much deeper. >> >> >> Lets say I now have two components, one displaying the items (so it is >> passed a cursor with path [:items]) and one displaying the orders (so it is >> passed a cursor with path [:orders]). What if I now only want to display >> items and orders where the type matches the filter? >> >> >> >> >> I have a few options: >> Restructure the app state in a way that gives each component access to what >> it needs. This is not ideal as it means that I'm modelling my state after >> how its being rendered rather than how its being processed and makes it very >> application specific. >> >> I can propagate the additional values down the component tree (eg using the >> :state parameter to build), but this means that every other component before >> the one that consumes it must now do additional work that it shouldn't need >> to know about (couples the parent components too tightly to the child one) >> >> Similarly, passing it in opts is not ideal as it has the same issue as #2, >> with the added caveat that the component also won't rerender on change.I can >> store the value in component local state and update it through a core.async >> channel. This works well in the example above, where one or two simple >> values need to be communicated, but gets unruly when the application is more >> complex. >> >> I can pass the entire app state to each component (perhaps trough shared >> state) and use transformation functions (similar to what Sean Grove did in >> his recent slides) to transform the state into a local view for each >> component. This means each component gets to select exactly what it needs to >> access without worrying about what comes before or after it in the >> hierarchy, but then you lose the benefit of cursors and automatic >> re-rendering when something changes. >> >> >> >> >> I'm sure I'm missing something! >> >> >> Any tips appreciated. >> >> >> Dan. > > -- > Note that posts from new members are moderated - please be patient with your > first post. > --- > You received this message because you are subscribed to the Google Groups > "ClojureScript" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/clojurescript. -- Note that posts from new members are moderated - please be patient with your first post. --- You received this message because you are subscribed to the Google Groups "ClojureScript" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/clojurescript.
