Compare Two Collections in a Flow

Question

Is it possible to loop through two collections and compare values?

I would like to look up values on the Contact object and compare them to values in a Custom Metadata object. The Contact object will be updated if mailing address data on the Contact Object matches data in the Custom Metadata Object.

I know that this could be done using fast look up and comparing one record at a time to the Custom Meta Data collection and maybe that is the best way? I am just used to using fast lookups for everything.

Answer 1

I think this challenge can be approached using string collection variables. It's tough to describe an imagined Flow, but I think it'd go something like this:

Fast Lookup for Custom Metadata Records
--> Loop over Custom Metadata Records
-----> For each record, add its key values (City, State, ZIP) to individual collection variables - i.e., one collection variable per data point you want to compare.

Source your Contacts (could be a Fast Lookup)
--> Loop over Contacts
-----> For each Contact, make a Decision
--------> If each key data point collection variable (City, State, ZIP) contains the
          value present on this Contact, update the data on this Contact as desired.

Perform a Fast Update of your Contact list.

I don't think you'll be able to approach it as comparing a list of addresses to a list of addresses; Flow doesn't have Address as an first-class type. You could do that in Apex with a Set of a custom class that implements hashCode() (although it wouldn't be an especially natural idiom there either).

Breaking it down into specific data points and ANDing criteria (listOfCities CONTAINS contactsCity AND listOfZIPs CONTAINS contactsZip AND...) is going to fit the bill for this application.