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FlowDeck integrates with LLDB-DAP to provide a powerful debugging experience for Swift applications directly within VS Code, offering features comparable to Xcode’s debugging capabilities.

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Features

  • Breakpoint Management - Set, disable, and manage breakpoints
  • Variable Inspection - Examine variable values during execution
  • Call Stack - Explore threads and the entire app call stack
  • Console Output - View application logs during debugging (OSLog)
  • Step Controls - Step over, into, and out of functions
  • Expression Evaluation - Evaluate Swift expressions in context

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Getting Started

1

Open your project

Open your iOS project in VS Code
2

Set breakpoints

Click in the gutter next to line numbers to set breakpoints
3

Choose target

Select your scheme and target (simulator or device)
4

Start debugging

Press F5 and select FlowDeck (LLDB) from the list

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Debugging Controls

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Toolbar Actions

  • Continue (F5) - Resume execution
  • Step Over (F10) - Execute current line
  • Step Into (F11) - Enter function calls
  • Step Out (⇧F11) - Exit current function
  • Restart (⇧⌘F5) - Restart debug session
  • Stop (⇧F5) - End debugging

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Breakpoint Types

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Standard Breakpoints

Click in the gutter or press F9 on any line.

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Conditional Breakpoints

Right-click a breakpoint and select Edit Breakpoint:
  • Expression - Break when condition is true
  • Hit Count - Break after N hits
  • Log Message - Log without stopping execution

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Exception Breakpoints

In the Breakpoints panel:
  • Add All Exceptions breakpoint
  • Add Swift Error breakpoint
  • Add Objective-C Exception breakpoint

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Debug Console

The debug console allows you to:
  • View application output
  • Execute LLDB commands (prefix with -exec)
  • Evaluate Swift expressions
  • Inspect variables with po command

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Useful LLDB Commands

po variableName           // Print object description
p variableName            // Print raw value
bt                        // Show backtrace
frame variable           // Show all local variables
thread list              // List all threads

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Variables Panel

The Variables panel shows:
  • Locals - Variables in current scope
  • Globals - Global variables
  • Statics - Static variables
Right-click variables to:
  • Copy value
  • Copy as expression
  • Add to watch
  • Set value

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Watch Expressions

Add expressions to monitor:
  1. Click + in Watch panel
  2. Enter Swift expression
  3. View updated values at each breakpoint

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Advanced Configuration

For custom debug configurations and launch options, see Debug Configuration.
Use the Debug Console tab during debugging to execute LLDB commands directly. Prefix commands with -exec for raw LLDB access.

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Tips for Effective Debugging

  • Use conditional breakpoints to avoid stopping unnecessarily
  • Watch key variables to track state changes
  • Check the call stack to understand execution flow
  • Use log points for non-intrusive debugging
  • Leverage LLDB commands for advanced inspection

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Troubleshooting

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Breakpoints Not Hit

  • Ensure Debug build configuration
  • Check optimization settings are disabled
  • Verify source maps are generated

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Variables Not Visible

  • Build with debug symbols enabled
  • Check you’re in Debug configuration
  • Ensure optimization is turned off

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Debugger Won’t Attach

  • Restart VS Code and simulator
  • Clean build folder
  • Check for conflicting debugger instances