Check if multi-select people picker has changed

[gj84uw]

Hi everyone

I have a list that contains an assigned to field which is a people picker field that accepts multiple selections.  I have created a flow with the trigger "When an item is created or modified" which then sends an e-mail to the user(s) in the assigned to field.  This works fine but sends the e-mail every time the item is modified even if the field hasn't changed.

I was thinking of creating a field called previous assigned and initially set this to the value of the assigned to field.  I could then check if the two fields match in the flow and if they don't, send the e-mail notification.  The only issue is I'm not sure how to do this with the multiple choice people picker?  If it was just a single choice field this would be simple but I'm not sure how I can compare a list of users in the multiple choice people picker with a text field?

[ScottShearer · Accepted solution]

@gj84uw 

A multi-select person or group column contains a collection.  So, one way to approach your issue is to loop through the collection and append each person selected to a string.  See my example below.  I have a multi-select person or group column called PG where I have entered two people.  The compose action at the end is there just to show the result - you won't need it if you implement this solution.  You can store the string in your additional column.  Then create a new string when the item changes to compare.

[SudhirSingare]

On page load collect
Collect(ColUsersOnPageLoad, ComboBoxUsers.AllItems)

Then on before submit code.

Collect(ColBeforeSubmit, ComboBoxUsers.AllItems)

and compare two colls: 
 If(Concat(ColUsersOnPageLoad, Email& ",") = (Concat(ColBeforeSubmit, Email & ","), ...


Then you can set hidden column in SPList: AreUsersUpdated = true or false, then this condition you can check before running flow action.

Note: For getting only new users from column is no straight forward as of now, this needs a lot of custom logic.