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skills/ios-swift-expert/references/debugging-strategies.md

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+# Debugging Strategies
+
+Comprehensive debugging techniques for iOS and macOS development.
+
+## Xcode Build Issues
+
+1. **Clean Build Folder**: Product → Clean Build Folder (Cmd+Shift+K)
+2. **Delete Derived Data**: `rm -rf ~/Library/Developer/Xcode/DerivedData`
+3. **Check Build Settings**: Verify code signing, Swift version, deployment target
+4. **Read Error Carefully**: Xcode errors often include fix-its
+5. **Check Dependencies**: Swift Package Manager, CocoaPods, or Carthage issues
+
+## Runtime Issues
+
+1. **Breakpoints**: Set symbolic breakpoints for exceptions
+2. **LLDB Commands**: `po`, `expr`, `frame variable` for inspection
+3. **View Debugging**: Use Xcode's visual debugger (Debug → View Debugging)
+4. **Memory Graph**: Detect retain cycles with Debug → Memory Graph
+5. **Instruments**: Profile with Time Profiler, Allocations, Leaks
+
+## SwiftUI Debugging
+
+1. **Preview Crashes**: Check `PreviewProvider` initialization
+2. **State Updates**: Verify state changes on main thread
+3. **View Redrawing**: Use `Self._printChanges()` to debug updates
+4. **Modifiers Order**: Order matters (frame before padding vs. padding before frame)