iOSDev UK: Beyond NSLog

Tim Isted, @timisted

NSLog, XCode and gdb

• useful macros for logging:
  • __FILE__ (full path)
  • __LINE__
  • __FUNCTION__ (and __PRETTY_FUNCTION__)
• NSStringFromSelector(_cmd) gives you current message
  • Lots of these useful NSString functions, e.g. NSStringFromCGRect
• use macros in log define
  • non-debug version should be something like: TILog(...) do {} while (0)
• XCode preferences > Behaviours
  • Run starts — can choose what displays
• XCode also has a variables view, hidden in the next pane of the debugger
• add breakpoints for exceptions or non-source code by using little plus button at bottom of breakpoints pane
• breakpoints have really useful options
  • log to console on hit (with auto hit count)
  • continue automatically
  • only do stuff on conditions
• gdb commands:
  • s = step = Step In
  • m = Step Over
  • c = Continue
  • p = Print
  • po = Print Object
• debugging Core Data: use [self valueForKey:@"propertyName"]
• can use addresses instead of variable names in po
• can make breakpoints user-specific instead of project-specific

Instruments

• Time Profiler — great for catching infinite loops!
  • shows you time spent at certain places in call stack
  • tick the “Show Obj-C Only” checkbox
  • look for purple user symbols!
• Heap Shot tool find leaks
• quite a few WWDC videos on Instruments