Deciding Between an Extension and a Custom Pattern
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In this lesson, you will learn:
- What a pattern extension is
- When an extension is enough
- Why the archiver needs a new pattern
🔁 Quick look back: Last time: Choosing an Existing CI Class Before Creating One. You learned how SNWR chose to create a class for the archiver.
1 The Problem: Two Ways to Customize, With Different Risks
You can add to a baseline pattern, or build a new one. Pick wrong and:
- Editing a baseline pattern breaks future updates.
- Building new when an extension would do wastes time.
👉 The fix: Extend when you only need extra data. Build new when nothing identifies the app.
2 Pattern extensions
Key term: Pattern extension
Extra steps added to a baseline pattern in a separate section, so the baseline itself isn’t changed.
Because the baseline isn’t edited, ServiceNow can still update it.
3 Choosing
| Situation | Choose |
|---|---|
| Known device, need one more field | Extension |
| Unknown app, nothing identifies it | New pattern |
| Baseline pattern has a bug | Check content updates, then raise it with ServiceNow |
⚠️ Heads up: Never edit a baseline pattern directly. Future updates may overwrite your change, or skip the update.
4 Project Clear View: How We Implemented It
📍 Situation: Two customization needs came up: one extra Linux field, and the archiver.
🧭 Decision: Use an extension for the field and a new pattern for the archiver.
🛠️ Steps we took:
- Priya wanted one extra field from Linux servers: an extension.
- The archiver had nothing to extend: a new pattern.
- Recorded both choices in the design.
- Planned the extension for after the archiver.
✅ What we verified:
- Neither choice edits a baseline pattern.
- Hana agreed both.
📁 Evidence: Customization choices recorded in DD-D06.
5 Quick recap
- Extensions add steps without editing the baseline.
- Build new when nothing identifies the app.
- Never edit a baseline pattern directly.
- Extensions keep ServiceNow updates working.
6 Check yourself
Think of your answer first. Then tap to check.
1 What is a pattern extension? Show answer
Extra steps added in a separate section, without changing the baseline pattern.
2 Why does the archiver need a new pattern? Show answer
Nothing identifies it, so there’s nothing to extend.
3 Why not edit a baseline pattern? Show answer
Updates may overwrite your change or be skipped.
Nice work! You can pick the right kind of customization. 🎉
Next up: Designing the Identification Section
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