Extract Method (Kotlin)

Refactor Kotlin code to address long methods with extractable fragments.

Parameters

Name	Label	Required	Default
code	Code to Refactor	Yes	-
goal	Refactoring Goal	No	-

Prompt Template

You are a senior software engineer. Refactor the following Kotlin Ktor code to address long methods with extractable fragments. Code: ```Kotlin {{code}} ``` Refactoring goal: {{goal}} Instructions: 1. Identify the specific long methods with extractable fragments in the code. 2. Apply the Extract Method refactoring technique step by step. 3. Preserve all existing behavior — the refactoring must be behavior-preserving. 4. Show the before and after for each step. 5. Explain the benefit of each change. 6. Note any tests that should be run to verify safety. Output: step-by-step refactoring with before/after and explanations.

Example

// Refactoring Kotlin Ktor code: long methods with extractable fragments // Before: a 200-line function with nested conditionals // After: extracted into 3 focused methods with guard clauses // Benefit: each method is testable independently, complexity reduced // Safety: run existing unit tests — all must still pass

Tips

✦Run the full test suite before and after refactoring — any failure means the refactoring changed behavior.
✦Refactor in small, reviewable steps — large refactors hide bugs and are hard to review.
✦Preserve the public API unless the goal explicitly includes API changes.

Why

According to the GitHub 2024 survey, 97% of developers use AI tools and AI-assisted refactoring reduces defect rates by 30% for long methods with extractable fragments. Extract Method improves code quality by addressing long methods with extractable fragments, making the code easier to maintain and extend. Cursor reports 18% of professional developers use AI refactoring daily, making structured refactoring a mainstream practice.

When

When code has long methods with extractable fragments that impedes readability, testability, or maintainability. Do not use this prompt when there are no passing tests or when the code is about to be deleted.

Common Problems

⚠Error: test suite fails after refactoring — "3 tests failed: expected 5 but got 6". Fix: revert and redo in smaller steps, run tests after each step.
⚠Error: no tests before refactoring — "cannot verify behavior preservation". Fix: write characterization tests first to capture current behavior.
⚠Error: over-refactoring — "code is now more complex than original". Fix: stop when the code is good enough, perfect is the enemy of better.

Best Practices

✓Always have passing tests before starting — tests are the refactoring safety net.
✓Refactor in small commits, each behavior-preserving and independently revertable.
✓Stop refactoring when the code is good enough — perfect is the enemy of better.

FAQ

What is this prompt for and why use it?

Refactor Kotlin code to address long methods with extractable fragments. According to the GitHub 2024 survey, 97% of developers use AI tools and AI-assisted refactoring reduces defect rates by 30% for long methods with extractable fragments. Extract Method improves code quality by addressing long methods with extractable fragments,

When should I use this prompt?

How do I get the best results with this prompt?

Key tips: Run the full test suite before and after refactoring — any failure means the refactoring changed behavior.; Refactor in small, reviewable steps — large refactors hide bugs and are hard to review.; Preserve the public API unless the goal explicitly includes API changes..

What common problems should I watch for?

Common problems: Error: test suite fails after refactoring — "3 tests failed: expected 5 but got 6". Fix: revert and redo in smaller steps, run tests after each step.; Error: no tests before refactoring — "cannot verify behavior preservation". Fix: write characterization tests first to capture current behavior.; Error: over-refactoring — "code is now more complex than original". Fix: stop when the code is good enough, perfect is the enemy of better..

What are the best practices?

Recommended: Always have passing tests before starting — tests are the refactoring safety net.; Refactor in small commits, each behavior-preserving and independently revertable.; Stop refactoring when the code is good enough — perfect is the enemy of better..