Debug.watch doesn't appear in elm-reactor

[aphorisme]

Sorry, if this is a duplicate, but haven't found something on this topic so far.

For Debugging purpose I want to use 'Debug.watch'. It looks as if I could just wrap it around a value I want to watch over time. So, in a naive try, I just did wrap it around my model:

> main : Signal Html

> main = Signal.map (view actions.address) (Debug.watch "UIModel:" model)

If I point to this app in the elm-reactor via the wrench, I still got the message "You don't have any watches!" Even when I'm trying to wrap other values, it keeps saying that.

What am I doing wrong?

[Janis Voigtländer]

I guess the problem is that you are trying to apply Debug.watch on a Signal, but it is meant for being applied to simple values (typically inside signals). Try this variant of your code:

main : Signal Html
main = Signal.map (\m -> view actions.address (Debug.watch "UIModel:" m)) model

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[Janis Voigtländer]

Or, if you prefer (and being syntactically closer to your original version):

main : Signal Html
main = Signal.map (view actions.address) (Debug.watch "UIModel:" <~ model)

​

[Janis Voigtländer]

Would my proposed change to the documentation of Debug.watch in this pull request have saved you some trouble?

​

[aphorisme]

Definitely. Thanks!
I would also like to propose that the message in the debug mode gets changed. That it kept saying: "You don't have any watches!" if I've added some (on a Signal) did confuse me a lot.

[Max Goldstein]

The "You don't have any watches" message more accurately means "The debugger has not received any watch messages yet". If you're watching a filtered or rarely-updating signal, it can be some time until a watch event comes through.

I support changing the message if it can be done unobtrusively, and the PR that's out to make it crash on signals.

[aphorisme]

Thanks  : )

[Pete Vilter]

Hi, I'm currently working on the reactor. I agree that "you don't have any watches" is sometimes misleading; filed a bug for that here and I'm trying to figure out how to fix it!

Also, I initially found it unintuitive that watching signals didn't work; I think that should work (perhaps with variant `Debug.watchSignal`). Will be thinking about this as well! Currently just trying to fix some basic reactor bugs, so probably won't get there for a while.

—Pete

On Wednesday, July 8, 2015 at 2:12:27 PM UTC-7, aphorisme wrote:

Thanks  : )