Add and Subtract from Dropdown Selected Value

[Anonymous]

Hello PowerApps Gurus,

I have been trying to figure out a way to do this for a couple of days now and can't seem to get it to do what I want.  I am building event app where users can select an event from the gallery and RSVP to the event from the detail page which is a form that contains a data card (dropdown) called Available Spots [1, 2, 3...15].  The number of spots is selected by the admin who creates the event.  In the detail form, there is another data card called Available Seats and I need for it to show the selected value from Available Spots and then as users register for that event, subtract 1 from the Available Seats.  Conversely, when they change their RSVP to "Not Going" I need 1 to be added back to the Available Seats.  

The forms are tied to one SP list called Eventfull Calendar and the attendees are on another SP list called AttendeeListSP.  Each attendee is a record on the AttendeeListSP.  

Can anyone please help?  I'm going mad!

[mdevaney]

@Anonymous 
You could use this code in the OnSuccess property of the form.  Replace the 1 with the ID number of your record.

With(
    {currentRecord: LookUp(your_datasource_name, ID=1)},
    Patch(
        your_datasource_name,
        currentRecord,
        {AvailableSeatsColumn: currentRecord.AvailableSeatsColumn-1}
    )
)

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[Anonymous]

@mdevaney

Thank you for such a prompt response.

Sorry for not being clear. I'm including a screen shot for your reference. When a new event is created, the form is submitted. When a user clicks RSVP button from the detail page, his/her info is patched to the AttendeeListSP list. You can see in my code where I have tried playing around with a variable and patching the value to the Eventfull Calendar SP list.  I'm not quite sure how I can use your solution with the way my app is set up.

[mdevaney]

@Anonymous 
It appears you have more than 100 errors in your app currently.  I think it would be a good idea to fix this before trying the solve the add & subtract problem.  Can you please do this?

---
Please click "Accept as Solution" if my post answered your question so that others may find it more quickly. If you found this post helpful consider giving it a "Thumbs Up." 

[RandyHayes]

@Anonymous 

Please provide the answers to the following questions:

1) In your AttendeeList:

    a) What type of column is Host?

    b) What type of column is EventID?

2) In your Form:

    a) What is the formula on DataCardValue14?

    b) What is RSVPToggleLabel12 Text formula?

3) Are you really trying to change the available seats on the master record (in EventFull Calendar)?  Seems that you would want to leave the available seats selected by the host as-is and simply tally the number of RSVP's in your AttendeeList to determine availability.

[mdevaney]

@RandyHayes 
I agree with your method.  But the user should 1st focus on fixing the 100+ errors, should they not?  Otherwise the solution might be derailed by one of these errors and we will never know why.

[RandyHayes]

@mdevaney 

Possibly, but I often find the count there very misleading as it is in many cases just a long list of warnings.

But as I looked at the formula provided, it was highly complicated and need not be.  And I had noticed some issues with the core function in it...thus the questions 😉

[Anonymous]

@RandyHayes ,

Hi Randy,  

Thanks for responding.  My answers to your questions are in bold below.  

Please provide the answers to the following questions:

1) In your AttendeeList:

    a) What type of column is Host?  Single line of text

    b) What type of column is EventID?  Number

2) In your Form:

    a) What is the formula on DataCardValue14?  This is the host data card.  Items Property is Choices([@'EventFull Calendar'].Host)

    b) What is RSVPToggleLabel12 Text formula?  If(Toggle2.Value = false, "Yes", "No")

3) Are you really trying to change the available seats on the master record (in EventFull Calendar)?  Seems that you would want to leave the available seats selected by the host as-is and simply tally the number of RSVP's in your AttendeeList to determine availability.  Yes, this is exactly what I wish to do.  I wish to leave the available seats selected by the admin as-is and tally the number of RSVP's in my AttendeeList to determine availability.  Conversely, when someone changes their RSVP, it should add back that seat to the Available Seats.

[Anonymous]

Please provide the answers to the following questions:

1) In your AttendeeList:

    a) What type of column is Host?  Single line of text

    b) What type of column is EventID?  Number

2) In your Form:

    a) What is the formula on DataCardValue14?  This is the host data card.  Items Property is Choices([@'EventFull Calendar'].Host)

    b) What is RSVPToggleLabel12 Text formula?  If(Toggle2.Value = false, "Yes", "No")

3) Are you really trying to change the available seats on the master record (in EventFull Calendar)?  Seems that you would want to leave the available seats selected by the host as-is and simply tally the number of RSVP's in your AttendeeList to determine availability.  Yes, this is exactly what I wish to do.  I wish to leave the available seats selected by the admin as-is and tally the number of RSVP's in my AttendeeList to determine availability.  Conversely, when someone changes their RSVP, it should add back that seat to the Available Seats.

[RandyHayes · Accepted solution]

@Anonymous 

I had additional questions on your overall app, but I believe I can assume some things.

It appears that you have a ViewForm (or EditForm in View Mode) and are not actually "submitting" the form on the screen shot you gave.  And, that you have an Image control for the RSVP action with an envelope_RSVP image on it.

You have stated that you do not wish to change the available seats in the EventFull Calendar list that was set by the admin/host and instead wish to tally the attendees in the AttendeeList.

I am assuming that you have some sort of logic for un-RSVP'ing.  I do not see that anywhere, but will speculate on it after addressing the RSVP part.

Based on that information, your formula in your Image control OnSelect should be:

Patch(AttendeeListSP, Defaults(AttendeeListSP), 
    {
      AttendeeName: Office365Users.MyProfile().DisplayName, 
      RSVP: If(Toggle2.Value, "No", "Yes"),
      Host: DataCardValue14.Selected.Name,
      EventName: DataCardValue1.Text,
      AttendeeEmail: Office365Users.MyProfile().Email,
      EventID: Value(DataCardValue20.Text)
     }
)    

This will add an Attendee record for the person using the app.  It is assumed that DataCardValue20 will contain the ID of the event, that your Host column in your EventFull Calendar contains a Name value, and that DataCardValue1 contains the Event Name (although it would not be needed in this list and is redundant.)

Also note in the above that you are not Patching or Updating the EventFull Calendar list - as you have stated you do not want to alter the admin/host allocation of seats.

To get the current number of available seats, you can utilize this formula:

With({aList:
    Filter(AttendeeList,
        EventID = Value(DataCardValue20.Text)
    )},

    EventListGallery1.Selected.AvailableSeats - CountRows(aList)
)

As stated, unknown to me is how you are dealing with someone cancelling their RSVP, but, I would suggest there is some button/image/etc. control you are using and it would be Visible based on this formula:

!IsBlank(
    LookUp(AttendeeList, 
        EventID=Value(DataCardValue20.Text) &&
        AttendeeEmail = Office365Users.MyProfile().Email,
        ID
    )
)

And the OnSelect action of that control should be the following formula:

RemoveIf(AttendeeList, 
    EventID=Value(DataCardValue20.Text) &&
    AttendeeEmail = Office365Users.MyProfile().Email
)

No other formulas (or variables) are needed to update the attendee count with all of the above as it will dynamically change the attendee count with the above formula.

As a side note, I don't really like the reliance on DataCardValue20 - if you have an EventID in the EventListGallery1 it would be better to replace the DataCardValue20 in the above formulas with EventListGallery1.Selected.EventID   If that particular EventID (or whatever it might be called) is numeric, then remove the Value functions in the provided formulas accordingly as you do not want to convert a numeric to a numeric (will not hurt but it is a waste).

The same goes for the DataCardValue14 and DataCardValue1 used in the first formula provided.  If these are already in the Gallery, then use those instead.

[Anonymous]

@RandyHayes

Sorry, I haven't been back sooner.  You're solution worked beautifully, Randy.  This is the code I used.

With({aList:
Filter(AttendeeListSP,
EventID = Value(DataCardValue20.Text)
)},

EventListGallery1.Selected.Available_Spots.Value - CountRows(aList)
)

Thanks again!