Hi Kasey, I just wanted to mention that the wikipedia article
Model-view-viewmodel
<https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93viewmodel> might
be helpful reading. In some architectural patterns this is called the
viewmodel rather than the model. (A couple of GUI oriented packages call
this State, for the same reason I think).
At my workplace we tend to use the convention that models should be named
after screen elements, e.g. PartEditor.Model whereas the response from the
server would just be called Part (even though this record is closer to the
database model).
-Editor, -Report, -Chart, -Table, -Matrix, -Page, -Viewer are of a couple
of suffixes I'm tending to reach for when naming the modules that contain
viewmodels.
On Saturday, April 22, 2017 at 7:18:41 PM UTC, Dustin Farris wrote:
>
> Interesting approach to just cache things in local storage and use the
> Model as a view "state" only.
>
> I keep a nice store in my Model, but I think a key difference is that I'm
> using websockets to update information automatically. Each route (page)
> has a list of channels that it cares about, and when data comes in on those
> channels, the store is updated.
>
> WRT your issue on authenticated routes, my approach was to write a
> function that checks the model for a Maybe String which is the JWT token.
> If it was Nothing, I'd send a Cmd to navigate to the login page. It has
> worked well so far.
>
>
> On Wednesday, April 19, 2017 at 7:28:06 PM UTC-4, Kasey Speakman wrote:
>>
>> I'm probably slow, but in recent months I've discovered that trying to
>> use Elm's Model like a database or cache (as I have previously seen
>> suggested) has turned out to be pretty painful for me. An example
>> database-minded model where a section could display *either* a list of
>> employees *or* a list of courses.
>>
>> type alias Model =
>> { employees : List Employee
>> , courses : List Course
>> , loadingError : Maybe Http.Error
>> , route : MyRoute -- employee or course
>> }
>>
>> The problem this runs into is having to worry about state management. I
>> have to remember to "reset" or "turn off" things when they are not active.
>> As my application grew, I had a lot of problems that boiled down to tedious
>> state management details. My cached data didn't turn out to be all that
>> useful because I usually had to reload it anyway, in case something changed.
>>
>> Instead, I have been moving toward the model only representing the
>> current state of my UI. The big difference here is the model representing
>> the current *visual* elements and their data. This leads more to using
>> union types to represent parts of the UI. When you switch to a different
>> case of the union type, the data from the previous case is *dropped on
>> the floor*. This leaves nothing to remember to "reset". RemoteData is a
>> good micro-example of this. If there was an error fetching the data, when
>> the user requests the data again, you switch back to Loading, the error
>> message is dropped on the floor. No forgetting to hide it.
>>
>> type RemoteData e a
>> = NotAsked
>> | Loading
>> | Failure e
>> | Success a
>>
>> If it is really important to cache the data, I prefer to keep that as a
>> persistence concern, not on Model. It can be part of the process for
>> retrieving the data to first check my chosen cache before making a request
>> for fresh data. For instance, first check local storage before making an
>> HTTP call. (Currently, this scenario is easier with Native modules for lack
>> of Local Storage API or being able to wait on port subscriptions. But it's
>> still doable.)
>>
>> So working towards a Model reflecting the visuals on the page has been an
>> interesting challenge. I'm not claiming it's easier, but so far I've found
>> it avoids a class of problems, and has led to some interesting discoveries
>> in my own apps. One small example: I realized that my LoggedIn and
>> NotLoggedIn routes should actually be separate "apps". Attempts to model
>> this in a SPA fashion with the LoggedIn and NotLoggedIn routes as siblings
>> always came up with the conundrum: how do I make it a compiler error for
>> the model to be in LoggedIn mode but I receive a NotLoggedIn message, or
>> vice versa? Even using TEA, I could not avoid this situation. Then I
>> realized the only way to do that would be as separate apps. And that it was
>> entirely possible to separate them. My "login page" turned out to be an
>> entirely self-contained process: the user filling in info, obtaining a
>> token, and saving it to local storage.
>>
>> I post this in the slim hope it is helpful to someone.
>>
>
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