Increment a number field in power Apps

[ChrisTu]

Hi 

I have developed my first Power app based on a sharepoint list and it was all going brilliantly until something happened which meant that 

If(Project_Details_Edit_form.Mode=FormMode.New,Last(Projects).UniqueID+1,Parent.Default)

stopped creating the right numbers both on live where I have around 60 records and it returns 48

and on test that has 4 records and kept returning 2

has anyone got any ideas -

interestingly the version I first created still works, 

just when i have created a new sharepoint list ( based on the original ) and then a new App ( by saving the App with a new name and changing the data source to the new list) it doesnt work even creating a new app over the original list doesn't work

I am at a loss as to what else to try 

Thanks 

Chris   

[RandyHayes]

@ChrisTu 

Please consider changing your Formula to the following:

Coalesce(Parent.Default,
    First(Sort(Projects, UniqueID, Descending)).UniqueID + 1
)

I am assuming your UniqueID column is numeric.

I hope this is helpful for you.

[Drrickryp · Accepted solution]

Hi @ChrisTu 

It looks like you are creating a custom ID field for your app.  If so, I strongly recommend not using Last() as it will give incorrect results if your list exceeds the maximum number of records in the advanced settings.  Make sure that the column type is Number and use

First(Sort(SPlist,UniqueID,Descending)).UniqueID+1 

as the default setting for the textbox in the UniqueID card in your form.  FYI, SharePoint already assigns an ID to every new record that it creates but @WarrenBelz  points out that there may be a good reason to create your own "Shadow ID" in his blog here. https://www.practicalpowerapps.com/delegation/power-apps-delegation-sharepoint/ ,  particularly, if you anticipate that your list will grow beyond the 2000 limit for delegation. The SharePoint supplied ID is only partially delegatable, while a custom ID column is fully delegatable. 

Your formula can be more concisely written as 

Coalesce(
         Parent.Default,First(
                              Sort(
                                   Projects,UniqueID,Descending
                              )
                         ).UniqueID+1
)

In a New form, the Parent.Default will always be blank so it will default to create the new uniqueID.  In Edit mode, there should always be a UniqueID so it will use the Parent.Default.  To make it work right, you may have to go back to SharePoint and fix the data in the UniqueID so that it is correct and then try the above in the future.  As an experiment, you could replace UniqueID in your formulas with simply ID and use the value supplied as metadata by SharePoint.  

[ChrisTu]

Thanks this seems to do the trick 

[RandyHayes · Accepted solution]

@Drrickryp 

[ChrisTu]

it doesn't seem to be saving back to the Sharepoint list with the other information ?? have i missed anything 

[Drrickryp · Accepted solution]

@ChrisTu 

Check the Update part of the card to make sure that it is picking up correct value from the control inside.  Actually, if you put that formula into the Update of the card, it doesn't matter what is in the control.  It also prevents the User from changing it. 

[Drrickryp]

@RandyHayes 
The Rest of Us.....................................Randy

[RandyHayes]

@Drrickryp 

[ChrisTu]

hi 

this works brilliantly until I decide not to progress with the New item 

In my app I click the New button on  the gallery 

I get a blank edit screen with the next ID number all good 

If I decide not to continue putting in the new details my X navigate button contains the following 

Navigate(Project_List, ScreenTransition.Fade) ( and takes me back to the Gallery ) without submitting card

however

when I then select a different item from my Gallery go to the display screen and then go to the edit screen for this item I get the New screen created in the earlier discarded action rather than the edit screen for the selected item

I assume I need some sort of "discard record" function but dont know what that might be  ????   

Thanks again everyone is being really helpful  and this really is the last step before I can make a big change to our project processes in diabetes UK