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0 points1_player5y ago0 comments

There's no need for client side prediction or optimistic UI on (most) Live View projects.

It's all done on the server.

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7 comments · 1 top-level

Latency is the reason. Even in a turn based game it still feels really bad to make a move and have to wait for it to make its way through the round trip before seeing the result. In a game with strict ordering like Tic Tac Toe there is little reason not to show the chosen move immediately.

1_playerOP5y ago

Sure, that's why I meant most use cases.

I mean, 100 ms between a click and a cross appearing on screen is not great user experience, but it's not even the worst. If you're writing a game, a little client side prediction is a good idea.

But if you have a form with instant validation, or any old regular UI, that is not necessary at all. The only built in optimistic UI functionality on Live View is disabling a button when you press it and wait for the server to respond, to avoid double submissions.

meheleventyone5y ago

> But if you have a form with instant validation, or any old regular UI, that is not necessary at all.

Arguably because you're trusting the client and essentially the built or built-in behavior is therefore optimistic by default. Then hopefully validating on submission server-side.

keymone5y ago

From the tech talks I vaguely recall, LiveView folks seem to disregard latency, which is where the entire model falls apart for me because the moment you need more control on the client over what to do when the server is not responding - you’re entirely out of luck.

Though maybe I’m wrong and there has been some new developments to address this, I wasn’t following too closely.

sfusato5y ago

On the contrary, LiveView documentation acknowledges this and suggests to handle such scenarios using client side tools:

There are also use cases which are a bad fit for LiveView: Animations - animations, menus, and general UI events that do not need the server in the first place are a bad fit for LiveView. Those can be achieved without LiveView in multiple ways, such as with CSS and CSS transitions, using LiveView hooks, or even integrating with UI toolkits designed for this purpose, such as Bootstrap, Alpine.JS, and similar.

https://hexdocs.pm/phoenix_live_view/Phoenix.LiveView.html#m...

1 more reply

Ndymium5y ago

Possibly many LiveView tech demos / projects by the community haven't had much thought into latency, but LiveView itself even contains a latency simulator[0] built-in. Additionally, it can toggle classes on elements when you click them and turn them off again when an acknowledgment has been received from the backend [1]. Finally you have the JS hooks, through which you can just implement any kind of loading indication you want on the frontend. So the tools are there, they just need to be used.

[0] https://hexdocs.pm/phoenix_live_view/js-interop.html#simulat...

[1] https://hexdocs.pm/phoenix_live_view/js-interop.html#loading...

conradfr5y ago

One trick I remember using (~two years ago, so early LV) when handling click events was to put everything async/not needed to reply in a spawn() function.

But yes as soon as you're on the internet you'll often feel the delay if your app is interactive.

The problem is that it's a bit random, because the network and the VM performances are never totally linear.

I remember implementing a countdown (using 1s send_after()) that would work fine most of the time, but sometimes there would be some hiccup and the countdown would stall just a bit and then process the counter in an accelerated fashion, which was terrible from a UI point of view, so in the end I did it in JS except for the update once the end reached.

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