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Kunal Kamble
Kunal Kamble

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Xcode debugging cheatsheet

This is a cheatsheet - starting point to look for things that you can do.
Avoided complex / 3rd party things as they require some additional setup that may not be allowed in certain projects.


  • Breakpoint is user enabled point in code where the application pauses
  • Line and column breakpoints
    • Pauses the program before the statement on line/column is executed
  • Conditions
    • Execute walk method just for LadyBug: self.bugType == 1
  • Actions: Sound, Log message, Debug command
  • Symbolic breakpoints: Add breakpoint on a method without source file [UIImage systemImageNamed:]
    • po $arg1 -> Receiver object
    • po $arg2 -> po (SEL)$arg2 -> Method name
    • po $arg3 -> First argument, and goes
  • Watch points: Pauses when the value changes

LLDB commands

  • help: Information about commands
  • v: Does not compile the expression instead it just dumps value from the stack
  • p: Evaluates and prints the output
  • po: Evaluates the print debug output
    • description method
    • Use [] syntax if . is failing due to typecasting
  • expression: Evaluates and prints, also stores the output in a variable
    • Expressions in other languages: expression -l swift/objc -O -- <code>
  • alias: Creates a shortcut for complex commands
    • command alias greet p @"Hello World"


  • Inject code without building it: expression <sample fix/feature>
    • expr [bugs addObjectsFromArray:[[self makeAntViews:20] mutableCopy]]
  • Short circuit / skip code execution:
    • Move the debugger handle
    • thread jump --by 1
  • Early return through a method: thread return <return value>
    • NOTE: This does not always work and can be dangerous
  • Print the view hierarchy: po [self.view recursiveDescription]
  • Highlight a view:
    • (UIColor *)[bug setBackgroundColor:UIColor]
    • (void)[CATransition flush]: Refreshes UI
  • Add delay in code: expr [NSThread sleepForTimeInterval:2]
  • Auto layout debugging: po [self.view _autolayoutTrace]


  2. Advanced lldb tricks for Swift - Injecting and changing code on the fly
  6. Leveraging Swift in Xcode’s LLDB

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