Announcing the 2025 State of Backstage report

Using the split function to process comma-separated strings

Published on August 28th, 2025

Template

Actions used

You can check the available actions if you visit /create/actions.

Walkthrough

Example Template

yaml
---
apiVersion: scaffolder.backstage.io/v1beta3
kind: Template
metadata:
  name: split-string-example
  title: Split comma-separated string and process each value
  description: This scaffolder takes a comma-separated string input and processes each value individually.
spec:
  owner: roadie
  type: service
  parameters:
    properties:
      things:
        title: Comma-separated list of things
        type: string
        description: Enter items separated by commas (e.g., "item1,item2,item3")
  steps:
    - id: log-each-string
      name: Log each string
      action: debug:log
      each: ${{ parameters.things | split(",") }}
      input:
        message: ${{ each.value }}

Breakdown

Parameters

This section configures the frontend for your template. The user provides a single string input that contains multiple values separated by commas.

yaml
things:
  title: Comma-separated list of things
  type: string
  description: Enter items separated by commas (e.g., "item1,item2,item3")

Steps

debug:log with split function

This step demonstrates how to use the Nunjucks split filter to convert a comma-separated string into an array, then iterate over each value using the each keyword.

yaml
- id: log-each-string
  name: Log each string
  action: debug:log
  each: ${{ parameters.things | split(",") }}
  input:
    message: ${{ each.value }}

The split(",") filter takes the input string and splits it at each comma, creating an array of individual strings. The each keyword then iterates over this array, making each value available as each.value.

How it works

  1. User enters: "apple,banana,cherry"
  2. The split(",") filter converts it to: ["apple", "banana", "cherry"]
  3. The each iteration processes each item:
    • First iteration: each.value = "apple"
    • Second iteration: each.value = "banana"
    • Third iteration: each.value = "cherry"

Use Cases

This pattern is useful for:

  • Processing lists of repository names, service names, or component names
  • Creating multiple resources based on a simple string input
  • Converting user-friendly comma-separated input into actionable data

Further reading