OnParametersChanged not triggered
Application Type
Service Studio Version
11.8.9 (Build 30789)
Platform Version
11.8.0 (Build 12006)

Hi all,

Have you ever met an issue that the OnParametersChanged event is not raised despite the value of the parameter has been changed? Some specifics:

  • this parameter is a structure; attributes of this structure are changed directly (I mean - as an opposite to creating a new structure object and setting it as the value of the variable)
  • the blocks' hierarchy is as follows: my screen contains a Block A that contains many Blocks B; the changing parameter is passed from the screen to Block A and Block A passes it to all Blocks B

It seems that under Firefox it always works well and the issue concerns only Chrome - and only sometimes.

I know that all this sounds mysteriously :-) I've tried to reproduce this behaviour in a simplified example but I've failed.

Thanks in advance for any hints and suggestions.



Hi Tomasz,

Good morning!

Were you able to check in the Developer tools of the Chrome via console if an error is being thrown?

Kind regards,


Hi Tomasz M. Lipinski,

I have tried to replicate this scenario, but no success. How did you perceive the problem? Using messages?

 Best regards

Hi, all,

@Christopher Bautista : no, I haven't checked it this way. You're right, my fault. Next time.

@Kadu Borges : Yes, I think it is just impossible to replicate this behaviour in a simplified scenario; I'm pretty sure that generally it works. The problem itself: first, the desired functionality stopped to work; then I've proved the reason using  log messages (LogMessage (Client)).

The worst thing is that it is not deterministic. Now it works with both browsers - just after adding some code, removing this code and publishing the solution several times. 



One reason that this can happen is if you have a block in an 'If' widget or are setting the visibility property. 

This works differently in Reactive than it did in Traditional. 'Visible' in Traditional used to work like "Visibility: Hidden". Now it works like an "If" widget and removes it from the DOM entirely.

If you are doing this, it's possible that the block doesn't exist in the DOM at the time you are changing the parameter. You can confirm by checking the console. 

The workaround is to use the style "Visibility: Hidden" tag instead of an 'If' widget or are setting the visibility property. 

Not sure if this is your case, but its a common misconception. If it is the case, let me know if you have a problem implementing.



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