How do you handle situations like this: Your application navigates to some route that involves loading some data. Lets say its a folder that may contain some images. Browser.Navigation.pushUrl key "/myapp/folder/1/" results in Browser.application.onUrlChange being called. The URL is parsed to ge…

Thinking about this some more, I realised my example works better the other way around. Suppose a user ends up at /myapp/folder/1/holliday-snaps.jpg, and bookmarks it because it is a nice picture. Later on they return to this bookmark, but the picture has been deleted. The application responds to a …

I don’t think this issue is particularly unique to Elm. It comes up lots of front-end frameworks. IMO, if fetching data is your bottleneck (and it often is), setting even fairly short cache times on the HTTP responses can go a long way to reducing duplicate network activity, even if the app thinks i…

We ended up applying a simple rule: All state changes and side effects that are linked to a url should be a reaction to the url change. Then, in the image example, just push the new url, and wait for Elm to react to this change. Many times we move side effects calls from update to init of a page bec…

In our framework we default to the load the world approach - i.e. a url change would call the page’s init function that would presumably load stuff from scratch (although our framework does support caching which can also mitigate this problem). However, for cases like this a page can opt in to inst…

[image] matt.cheely: I don’t think this issue is particularly unique to Elm. It comes up lots of front-end frameworks. IMO, if fetching data is your bottleneck (and it often is), setting even fairly short cache times on the HTTP responses can go a long way to reducing duplicate network activity,…

[image] rupert: I am thinking that checking for a duplicate route is best done on the Route and not the application Model (or page State or however you model your state)? What if you have a route that every time you access it gives you random dice throw. Then it makes sense to allow for dupli…

Something along the lines of: type Route = ShowImage Folder ImageId | RollDice | ... dedupeNavEvent : Route -> Route -> Bool dedupeNavEvent current proposed = case (current, proposed) of (ShowImage folder1 image1, ShowImage folder2 image2) -> Folder.isEqual fo…

I wrote a bit about this here a couple months ago: [image] "Route reuse" + looking for general advice Learn I’ve found the onUrlRequest / onUrlChange bifurcation in Browser.application to be really tedious to work with. It’s better than it was in 0.18, but still doesn’t …

The “philosophically” section of the elm-route-url readme has some good discussion and links too.

Using the URL both as a snapshot of the navigation state and as a source of truth for the navigation state looks like a bidirectional binding, which I something that I try to avoid as much as possible. In which situations do you see it as an advantage?

Routing when you already there

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jerith December 12, 2021, 3:07am 9

I wrote a bit about this here a couple months ago:

Topic		Replies	Views
"Route reuse" + looking for general advice Learn	13	1858	November 12, 2021
Understanding the "double update" behavior of Browser.application Learn	12	2178	February 6, 2019
Solving Elm Router "Double Update" Problem Show and Tell	5	317	October 4, 2025
What is the Elm 0.19 equivalent of Navigation.modifyUrl Learn	3	982	December 6, 2018
Do I have to save current URL into model if I want to use Nav.pushUrl? Learn	2	553	March 31, 2022

Routing when you already there

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