Canvas App - Clear Fields Based on Choice Column Answer

[Rubber_Duck]

Hi all,

I'm very new to PowerApps, so I'm helping someone can help me.

I have a Canvas App built from a SharePoint Custom List. The app contains a choice field, which includes only two options - 'yes' and 'no'. A number of subsequent fields (another choice field, a multi-line text field and a date/time field) are set to only become visible when the 'yes' option is selected in the initial choice field. This is working fine.

The problem I have is finding a method of clearing/resetting the three subsequent fields if the user later edits the form and changes the initial choice field to 'no'. The subsequent fields are being re-hidden successfully in this scenario, but they still contain the data from the initial submission. 

I've tried using an If condition to change the Reset property on the subsequent fields to 'true' when the value of the initial choice field is 'no', but this doesn't seem to work. 

This is stopping me from being able to use the app, so if someone can help me solve it it would be big help.

Thanks.     

[Low_Flying_Bird]

Hi Warren,

Thanks for replying. Much appreciated.

I had tried just using varReset on the Reset property, but being new to variables I had just followed your proposed steps in order, so it wasn't accepted. I've now done it after applying the If function to the trigger field first and it has worked.  

The additional fields still aren't being cleared when the trigger question is changed to 'No' though. The previous text, selection and date is still retained in the form fields and the SharePoint list.  

[WarrenBelz]

Hi @Low_Flying_Bird ,

You just need to have the Reset on all the relevant controls set to varReset

Run the Variable reset

UpdateContext({varReset: false});
UpdateContext({varReset: true})​

and all these controls will be reset to their Default value (note if they have a Default, they will not be cleared, just returned to their Default value

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[Low_Flying_Bird]

Thanks Warren. You are being very patient and I appreciate it.

I have now done the following:

On the OnChange property of the trigger field I have added - 

If(
   Self.Selected.Value = "no",
   UpdateContext({varReset: false});
   UpdateContext({varReset: true})
)

On the Reset property of the fields I need to be cleared if the trigger field is changed to 'No' I have added -

varReset

On the OnVisible property of the EditScreen I have added:

UpdateContext({varReset: false})

It still doesn't work I'm afraid. If I change the trigger field answer from 'yes' to 'no' via the edit form it hides the associated fields (which is where I had got to originally) but it doesn't clear the previous answers from those fields in either the form or the SharePoint list. 

[WarrenBelz]

Hi @Low_Flying_Bird ,

I assume the fields to be cleared are on the same screen as the control that triggers the reset? If so, it simply has to work (I have never experienced it not doing so). Put a Label with varReset on the screen and see if it changes from false to true when you change the trigger.

[Low_Flying_Bird]

Hi Warren,

Updating each of the fields, to include the code snips in my previous message, isn't working. None of the previous data in the associated fields is being cleared when the trigger is changed from 'Yes' to 'No' and the same applies to the SharePoint list (where the only change is the trigger answer - all other previous data is being retained).

I don't understand your point about the label test I'm afraid. To which property on the label am I adding varReset?      

All of the fields are definitely on the same screen by the way, yes. I'm making the adjustments on the EditScreen.

I've attached snips of each change made for reference (the Associated Reset has been applied to all three associated question fields) .

[WarrenBelz]

Hi @Low_Flying_Bird ,

I was simply testing if the variable was being set to true - if you have a label with the Text of varReset, it will display true or false as the variable is changed. Also try with a button on the screen

UpdateContext({varReset: false});
UpdateContext({varReset: true})

and see if that resets the fields. NOTE a reset is to their Default value, so what is the Default ?

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[Low_Flying_Bird]

Hi Warren,

Sorry for the delay in replying. A UK/Australia time difference thing I think!

The default for the date field and the multi-text field is Parent.Default. The default for the Choice column is blank. 

I appreciate the help you've tried to give me. I'm not an experienced developer though and this is becoming  complicated for what I anticipated would be a simple fix. To hide certain fields and only make them visible based on the selection in a choice field was very simple. To then clear those fields, and the associated columns in the SharePoint list, if the trigger selection is then changed really isn't. 

I've followed all of the steps you have suggested (apart from the button/label tests) and when the trigger question is changed to 'No', the hidden fields aren't being cleared or returned to their default and the data remains in the SharePoint list. The snips attached evidence that.

I'm sure it's down to my lack of understanding in some way. Probably time for me to admit defeat I think and see if someone in my company's IT team can help 🙂.         

[WarrenBelz]

Hi @Low_Flying_Bird ,

You are correct in that this is a really fundamental function and simply should work

• The Reset function a control triggers when the event specified in this function is satisfied
• In this case, the value of varRest (which is a Boolean true/false variable) infers it is changed to true (which is why I wanted to see a label on the screen to ensure the Variable was being set to true when your trigger was initiated and why I wanted the button to see if changing it to true directly would reset the controls).
• When this happens, the control is reset to its Default value (which is why I asked for the Default)

There is something clearly different here to what you believe is the case and I am trying to isolate it.

[Low_Flying_Bird]

Hi Warren,

Apologies for the delayed response. I was away from work for a period.

Since your last message (and thank you again for your ongoing support - it is very much appreciated) I have spoken with colleagues in our IT team. I figured my inexperience with Power Apps and variables was potentially causing the problem! 🙂

Unfortunately they haven't been able to clear data from the associated fields, and the SharePoint list, when the trigger question is changed to 'No' in the Power App either.

They advised that 'Changing the value of an already saved item based on the OnChange property of a dropdown isn’t something that can be done on PowerApps, due to the use of update context which updates the list with the immediate change' and that 'The update context updates the data source, so once that’s triggered the list is updated and if you change the value back to “Yes”, the updated field value will return null because that’s its new value.'

Does this sound right? What I imagined would be a really simple process, is turning out to be at best very complicated and at worst potentially not possible at all.

I have also tried your suggestion of adding a text input to the page with varReset as the default. This isn't changing from 'false' to 'true' when the trigger question is changed from 'Yes' to 'No'. 

Thanks again for your help.  

[WarrenBelz]

@Low_Flying_Bird ,

You are right that this is going on far too long for such a simple issue and the waters are getting more muddied the further we go here. You wanted a control reset and what I provided should do this. A reset control (to I assume blank) will clear the attached field once the new contents is saved to the data source, however your issue seems to be the Variable and you need to sort that before we can go any further.