💡 Signals API – Feedback & Discussion

[mshabarov]

This issue is for collecting any kind of feedback on the Signals API:

• API or design suggestions
• Bugs or unexpected behavior
• Real-world use cases
• Documentation or clarity issues
• Open discussion and questions

Related design document: vaadin/platform#8366

Even short feedback is valuable. If possible, please include a concrete example.

Description

Clearly describe your feedback.

• What feels good or problematic?
• What is confusing or missing?
• What would you like to change or improve?

Use case

Describe the real-world scenario where this matters.

Why is this important in practice?
How would developers benefit from a change here?

Code example (if applicable)

Minimal reproduction or illustrative example.
Pseudocode is perfectly fine.

const count = signal(0);

effect(() => {
  console.log(count.value);
});

Expected behavior

Describe a behavior you expect from existing API in case I doesn't work or look like you'd want.

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Remember to vote feedback comments so it helps us to prioritize future work.

[mshabarov]

Style Bindings

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Description

The current style binding API shape feels a bit unintuitive when binding a boolean signal to a style property. The argument order makes it harder to read and discover, especially when compared to existing Vaadin APIs.

Use case

When styling components based on a boolean state, developers expect a fluent and readable way to bind styles directly to signals without mentally reordering parameters.

Example

component.getStyle().bind(booleanSignal, "color", "green", "red");
// or
component.getStyle().bind("color", booleanSignal, "green", "red");

Thoughts / Questions

There are many places where one would want to pick one value or the other based on a boolean signal.

[HerbertsVaadin]

List Signal:

1. Requesting a way of getting all the raw values.
   For example, my initial expectation was that listSignal.value() will return a List<String> (if Signal is of String value type) , but it returns List<ValueSignal<String>> which is ok. But expectation is that there would be a method to get all the raw methods, so I could work with it.
   Instead my code has to look like this:

berlinTimelineSignal.value().stream().map(Signal::value).toList()

2. Requesting removeFirst(), removeLast()
   Since there's insertFirst(..) and insertLast(..), I expect to also for it to have equivalent remove methods, as well as get methods.
   I have a scenario where I'm updating a chart data series, and only want to display 12 latest values, thus I have to remove the oldest value, and add the newest. It looks like this:

if (londonTimelineSignal.value().size() >= TIMELINE_POINTS) {
       londonTimelineSignal.remove(londonTimelineSignal.value().getFirst());
}
londonTimelineSignal.insertLast(randomBetween(420, 820));

3. Requesting ability to replace all values.
   Since I can insert new values, and remove old values, I expect there to be a method to replace all at once (for example: listSignal.value(myValues). Now I must do:

listSignal.clear()
myValues.forEach(listSignal::insertLast);