How to Call a Script Include in a Custom Action Using Flow Designer

[BillMartin]

Calling a Script Include from Flow Designer may seem straightforward — but doing it cleanly and reusably takes a bit of thoughtful structure. In this article, I’ll share a developer-friendly approach that keeps your code maintainable, secure, and scalable.

Why Script Includes Matter in Flow Designer

If your custom Flow Action includes all the logic inside the Script step, it may work now — but it becomes hard to maintain and reuse later. Instead, delegate your business logic to a Script Include. This lets you:

• Reuse your logic across multiple flows

• Keep Flow Designer focused on orchestration

• Maintain separation of concerns

• Make your application more testable and secure

What We Did

In this solution, we:

1. Created a custom Flow Designer Action with defined inputs (e.g., employee details).

2. Created a Script Include (EmployeeFlowAPI) to handle the Flow’s request.

3. Delegated logic to a service layer (EmployeeServiceWrapper) with validation, logging, and insert logic.

4. Used an EmployeeEntity class to enforce data structure, validation rules, and automatic unique ID generation using GlideGuid().

5. Implemented logging via a shared BaseLogger class for consistent debugging and tracking.

Security & Data Integrity

The validation logic lives in the EmployeeEntity, so every request (from Flow, API, or other sources) is processed with consistent checks. This protects your logic from malformed data and simulated attacks — right at the edge.

Example Use Case

A flow triggers when a new request is submitted → it passes employee data into the custom action → the action calls EmployeeFlowAPI.createEmployee() → and the entity is validated and stored using a reusable service pattern.

Why It Works

• You get modularity and readability

• All logic is testable and reusable

• Changes only happen in one place, even if multiple flows call the same logic

• You future-proof your architecture as your system grows

Watch the Demo

If you're interested in seeing the entire setup from Flow Action to Entity and Service Layer, check out the full walkthrough on my YouTube channel:

Let’s Chat

Are you currently using this pattern? Do you pass raw inputs from Flow directly into your logic? I’d love to hear how you’re structuring your own reusable architecture.

Let’s share strategies and build more secure, scalable solutions together.