Roadie

Using for Loops to repeat scaffolder steps

Published on January 26th, 2024

Template

Actions used

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

Walkthrough

Example Template

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---
apiVersion: scaffolder.backstage.io/v1beta3
kind: Template
metadata:
  name: loop-template-example
  title: Loop through items to repeat a scaffolder step
  description: This scaffolder takes user input and loops through those into a log output.
spec:
  owner: roadie
  type: service
  parameters:
    properties:
      things:
        title: List of things
        type: array
        items:
          type: string
          title: A thing
  steps:
    - id: log-message
      name: Log Parsed Contents
      each: ${{ parameters.things }}
      action: debug:log
      input:
        message: 'contents: ${{ each.value }}!'

Breakdown

Parameters

This section configures the frontend for your template. Essentially these values will be provided from the backstage ui to the template.

This renders a list of input fields where you can input a string value. The value of these string is stored into an array which is called things

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things:
  title: List of things
  type: array
  items:
    type: string
    title: A thing

Steps

debug:log

Logs the contents of the file which was parsed in the previous steps. Uses the form input things and outputs a debug log line for each value.

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- id: log-message
  name: Log Parsed Contents
  each: ${{ parameters.things }}
  action: debug:log
  input:
    message: 'contents: ${{ each.value }}!'

Further reading