Apex-Defined Types in Flow in Plain English

 It's pretty opaque how Salesforce handles Invocables when using an Apex-defined type.

In my use case I am trying to create a generic utility that returns a bunch of stuff that you can't get in Flow. Achieving this is pretty unforgiving and I found it very confusing, so here's my attempt to demonstrate it in plain English.

Part 1: The Response

You need a standalone Class for the Response. In this case, I populate the values in the constructor. Note that the variables are both @AuraEnabled and @InvocableVariable. The @AuraEnabled allows the Class to be recognized as an Apex-defined type in the Flow.

 

 

Part 2: The Invocable Method

Your Invocable method takes an input, in our case a List<FlowUtilityRequest>. You will receive a list with a FlowUtilityRequest for each record your Flow is processing. So if the Flow runs with 100 records, you'll get a list with 100 copies of the Request.

The Response is sent in a List<List<FlowUtilityResponse>>. The size of the outer list needs to be the same as the number of records that are being processed -- this is reflected in the size of the input list.

You need to stage the outer list as if each inner list is being applied to one record. Imagine that when the data hits the Flow, it's iterating over each outer List item and applying the inner list to that record.

The inner list can contain whatever you want. Since in this case I am trying to return a few pieces of information that apply to everything, I need to:

  1. Gather the data I want to return into a variable called resultSingleObject.
  2. Create an innerList and add that resultSingleObject to it. The inner list is size 1.
  3. Create an outerList and add one copy of innerList for each record I'm processing. 

Part 3: The Flow

When the data comes back to the Flow, Salesforce is very picky about its format. Once you're in the Flow, you can ignore the outer List, because the Flow builder is relative to one record. Basically, imagine Salesforce is iterating over a list of your records and you are looking at one particular one.
 

Invoking the Apex Action

Invoke the action normally. In my case, I needed to manually assign the output to a Collection of my Apex-defined FlowUtilityResponses. In other words, I needed to make a variable with type = Apex-Defined, Class = FlowUtilityResponse.
 
If I tried to use the standard "Output from .." variable, when I went into the loop later, the Flow did not understand the data type contained in "Output From". 

Create a Variable:

 
 
Assign it in the Apex Action:

 

Once the Apex Action is invoked, the apexFlowUtilityResponseList contains one item in the list, of type FlowUtilityResponse. But since it's a list, we need to loop over it.

 I've made another variable, flowUtilityResponse containing one FlowUtilityResponse (i.e., not a Collection). I assign it in the loop. Because we know there's just one record, we'll only go through the loop once.

Flow

Loop Definition

Assignment Definition

Once that's done, we can use the flowUtilityResponse single variable and its components in other Flow components such as decisions.


  Using the response from Apex in a Flow component    



I hope all that makes sense. If you have any questions please hit me up on Bluesky.

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