How can duplicate code be identified in a project?

1. Visual analysis. Manual review of the codebase.
2. IDE plugins. For example, Duplicate Finder for AppCode or a plugin for Xcode, if available.
3. Static code analyzers. Tools like SonarQube or SwiftLint (with configured rules) can detect duplication.
4. Specialized tools.
   • PMD (Programming Mistakes Detector): Originally for Java, but there are adaptations or similar tools for Swift.
   • Simian (Similarity Analyzer): Compares source code for duplicate fragments. Supports many languages.
   • DupCode: A tool for finding duplicates in various programming languages.
5. Writing scripts. Scripts in Python, Ruby, or other languages that parse project files and compare code fragments or string hashes.

Examples of tool usage:

# Example of using SwiftLint to check for duplication (requires rule configuration)
swiftlint --strict // Search for duplicates based on configured rules

# Example of using Simian for analyzing Swift files
simian -language swift **/*.swift

Typically, a combination of methods is used for more comprehensive duplication detection and subsequent refactoring.