gof-prototype

One-line summary

Create new objects by copying an existing instance (the prototype) rather than by calling a constructor — useful when construction is expensive, when you only want to vary a few fields, or when you have a registry of canned shapes.

When to use this skill

• Object construction is expensive or has side effects that you don't want repeated.
• You have a "template" instance and want variations of it with a few fields changed.
• You need a registry of canned instances that consumers can clone and customize.
• The canonical Kotlin manifestation: data class.copy(field = newValue) is exactly this pattern.

When NOT to use this skill

• Construction is cheap and stateless — just call the constructor.
• The "copy" must be a deep clone of a complex object graph — Prototype's contract is usually a shallow copy; deep cloning is its own problem.
• You're trying to dodge a hard construction problem by "copying" something that doesn't really exist yet — that's a smell.

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