Deducting count from Sharepoint

[TheHockeyGeek]

I am trying have an app for checking out materials and when I run the following... it removes from all items on the SharePoint list. It functions with a collection behaving as a cart, and upon confirmation I want to deduct one from stock (SharePoint number column) for each. What's happening is that every item on the SharePoint list is deducting the 1 from every item in the collection from all items on the SharePoint list.

ForAll(colShoppingCart,UpdateIf('Consumable Inventory',Code=ThisRecord.Code,{Stock: Stock - 1}))

[RandyHayes]

@TheHockeyGeek 

To start, your formula has the ForAll backward. You are trying to use it like a ForLoop in some development language - which PowerApps is not.  ForAll is a function that returns a table of records based on your iteration table and record schema.

It is more efficient to use the function as intended and will provide better performance especially with an UpdateIf which is already very poor in performance!

Please consider changing your Formula to the following:

Patch('Consumable Inventory',
    ForAll(colShoppingCart As _cart,
        With({_item: LookUp('Consumable Inventory',Code=_cart.Code)},
            Patch(_item, {Stock: _item.Stock - 1})
        )
    )
)

I hope this is helpful for you.

[TheHockeyGeek]

Thank you for your reply! Ahh, that makes sense! 

The sample you sent did work quite nice actually! It did only remove 1 from each item even if it was on the list more than once. However, that's something I'm working on getting the cart to reflect a quantity rather than listing items more than once. The team uses a barcode scanner pulling items from a shelf so it's easier to continue scanning to increment the quantity.

[RandyHayes]

@TheHockeyGeek 

Glad that worked!

I am a little confused on what issue you are facing now?  Are you stating that the list is updating but the app is not reflecting it?  If so, that is because you are using a collection.

Or are you stating something else?

[TheHockeyGeek]

The collection will list items multiple times based on the scans; it only deducts one from each rather than multiples.

Collection

Item 1

Item 1

Item 1

Item 2

Item 3

Item 2

Sharepoint Before Execution

Item 1 - 50

Item 2 - 50

Item 3 - 50

Sharepoint After Execution

Item 1 - 49 (should be 47)

Item 2 - 49 (should be 48)

Item 3 - 49 (should be 49)

[RandyHayes · Accepted solution]

@TheHockeyGeek 

Ah...then in that case:

Patch('Consumable Inventory',
    ForAll(
        GroupBy(colShoppingCart, "Code", "_items") As _cart,
        With({_item: LookUp('Consumable Inventory',Code=_cart.Code)},
            Patch(_item, {Stock: _item.Stock - CountRows(_cart._items)})
        )
    )
)