feat(signals): add signalMethod

[rainerhahnekamp]

signalMethod is a factory function to process side effects on Signals or static values.

It is similar to rxMethod but does not support RxJS.

signalMethod follows Angular's pattern of RxJS-less utilities for Signals, like resource and rxResource.

signalMethod expects a type and processor function:

const doubleLogger = signalMethod<number>(value => console.log(value * 2))

const value = signal(1);
doubleLogger(value); // tracks value and executes initially and on every change

It also supports static values, e.g., doubleLogger(1).

This PR also contains the documentation and tests.

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/main/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

Closes #4581

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

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[timdeschryver]

LGTM 👍

I just left some comments on the docs.
Also, do we want to add a section similar to https://deploy-preview-4597--ngrx-io.netlify.app/guide/signals/rxjs-integration#reactive-methods-without-arguments?

[rainerhahnekamp]

@timdeschryver

Also, do we want to add a section similar to https://deploy-preview-4597--ngrx-io.netlify.app/guide/signals/rxjs-integration#reactive-methods-without-arguments?

We can but then we should also maybe provide a good example. Any ideas?

I was thinking about some reset function which is triggered if a Signal<number> changes?

const userId = signal(1);

signalStore(
  withMethods(store => ({
    reset: signalMethod<void>(() => patchState(store, initialState);
  })
)

[timdeschryver]

@rainerhahnekamp that's a good question 😅.

Initially I was thinking about a console.log (as with the effects example on angular.dev), but that isn't very useful.

I like the reset example, but then what is the difference between a "normal" method and a signalMethod?

signalStore(
  withMethods(store => ({
    reset: signalMethod<void>(() => patchState(store, initialState)),
    // compared to
    reset2: () => patchState(store, initialState),
  })
)

If we can't think of a good example, then maybe it isn't useful to create a withMethod without any arguments.

[rainerhahnekamp]

@timdeschryver

I like the reset example, but then what is the difference between a "normal" method and a signalMethod?

If you have

const userId = signal(1);

store.reset(userId);
store.reset2(userId);

Both will run once, but reset will then also execute whenever userId changes.

[timdeschryver]

Yes, but that's with an argument.

[rainerhahnekamp]

@timdeschryver

Oopsi... then I’m actually running quite short on examples!

Then I'll guess if we don't see a need for it, we don't need to mention it in the docs?

[timdeschryver]

Sounds good to me @rainerhahnekamp , we can always update it later if needed.

[markostanimirovic]

Great work Rainer! 👏

The implementation part looks good to me. 👍 I left suggestions for documentation:

[rainerhahnekamp]

@markostanimirovic, as always also thanks for your thorough review. I've committed all your suggestions and moved the 2 destroying tests to their suite.

[rainerhahnekamp]

@markostanimirovic I committed all your requested changes except one. I can't figure out what you meant here: #4597 (comment)

[timdeschryver]

👏👏👏

[markostanimirovic]

🚀