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Advanced iOS Debugging

Advanced iOS Debugging

The debug process constitutes an important part in an app's development cycle. Knowing the (right) tools and techniques means you can optimizes time and therefore costs. In this session we will see a number of techniques to optimize debugging of iOS applications exploiting the power of Xcode, LLDB and other support tools.

Massimo Oliviero

March 23, 2013
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  1. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Massimo Oliviero

    Freelance Software Developer Co-founder of #pragma mark http://pragmamark.org Online web http://www.massimooliviero.net email [email protected] twitter @maxoly slide http://www.slideshare.net/MassimoOliviero
  2. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Agenda •

    Code, some tips for standard functions • Xcode, the best tools for debugging • LLDB, your great friend • Tools, network debugging how to and more • Remote, over the air debugging
  3. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly It all

    began... NSLog(@"Error :( %@", error); NSLog(@"User: %@", user); NSLog(@"Array: %@", array); NSLog(@"URL: %@", url); NSLog(@"Count: %i", count); NSLog(@"User %@", user); NSLog(@"Array %@", array); NSLog(@"Error :( %@", error); NSLog(@"Error :( %@", error NSLog(@"URL: %@", url); NSLog(@"Array: %@", array); NSLog(@"User: NSLog(@"User: %@", user); NSLog(@"User: %@", user); NSLog(@"User: %@", user); NSLog(@"User: %@", user); NSLog(@"User: %@", user); NSLog(@"User: %@", user);
  4. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly NSLog •

    It prints debugs output only to the console • It’s a simple native Foundation function • It’s not too bad, but It’s an ancient technique • It slows things down considerably (if not handled)
  5. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly NSLog optimization

    • Use convenient macro • Use string conversions • Try alternative frameworks
  6. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly NSLog macro

    #if defined DEBUG #define MYNSLog(s, ...) NSLog((@"%s [Line %d] " s), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__) #else #define MYNSLog(s, ...) #endif -[TestViewController viewDidLoad] [Line 33] message - (void)viewDidLoad { [super viewDidLoad]; MYNSLog(@"message"); } MyGreatApp-prefix.pch TestViewController.m Console
  7. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly NSLog macro

    • Enables DEBUG mode output only • Outputs function name and line number • Place macro into .pch file or in a header file • You can use other macros like __ FILE__ (for example)
  8. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly String conversion

    functions CGPoint point = CGPointMake(10.5f, 12.3f); NSLog(@"point: %@", NSStringFromCGPoint(point)); AdvanceDebuggingExample[3050:c07] point: {10.5, 12.3} AdvanceDebuggingExample.m Console
  9. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly String conversion

    functions Returns a string formatted to contain the data from a structure: • NSStringFromCGAffineTransform • NSStringFromCGPoint • NSStringFromCGRect • NSStringFromCGSize • NSStringFromUIEdgeInsets • NSStringFromUIOffset
  10. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Try alternative

    frameworks • CocoaLumberjack https://github.com/robbiehanson/CocoaLumberjack • NSLogger https://github.com/fpillet/NSLogger • DMLogger https://github.com/malcommac/DMLogger
  11. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Xcode •

    Configure your Behaviors • Print more information with Arguments • Go beyond logging with Breakpoints
  12. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Xcode Behaviors

    • Match Xcode to your Workflow • Use Behaviors to control Xcode • Behaviors lets you specify what should happen when a variety of events occur (like Run)
  13. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Change default

    Behavior For example, when Running pauses: • show the Breakpoint Navigator instead of Debug Navigator • show only Variable Views • open another tab only with Console view
  14. Breakpoint action Condition to evaluate The num of time to

    ignore breakpoint before stoping Log Message Action Debugger Command Action Play sound Continue program execution
  15. Sharing Breakpoint Share breakpoints with the team, so that all

    can benefit from it This action will create a new directory to be committed in the repository AdvanceDebuggingExample.xcodeproj/xcshareddata/
  16. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Why LLDB

    • Consistent Command Syntax • Scriptability with Python • Performance • ...
  17. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly LLDB Commands

    print object po [object] print variable print [variable] assign value expr [variable] = [value] (lldb) <command>
  18. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly LLDB Commands

    set breakpoint breakpoint set -f [file] -l [line] load script command script import ~/test.py evaluate expression expr <expression> <noun> <verb> [-options [option-value]] [argument [argument...]]
  19. Custom object, the problem No summary for custom object @interface

    ADEEvent : NSObject @property (nonatomic, strong) NSString *title; @property (nonatomic, strong) NSDate *when; @end ADEEvent *event = [[ADEEvent alloc] init]; event.title = @"Codemotion Conference"; event.when = [NSDate date]; Init object Custom object
  20. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Custom summary

    • Create a Python script that will instruct LLDB on how to display a summary of your custom object • Load your Python script via command line or ~/.lldbinit file
  21. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Custom summary

    import lldb def ade_summary(valobj, internal_dict): ! titleAsString = valobj.GetChildMemberWithName('_title').GetSummary() ! whenAsString = valobj.GetChildMemberWithName('_when').GetSummary() ! return 'Title: ' + titleAsString + ' - when: ' + whenAsString def __lldb_init_module(debugger, dict): debugger.HandleCommand('type summary add ADEEvent -F CustomSummaries1.ade_summary') • Create “ADEEvent_summary.py” in Xcode project • Then load script: (lldb) command script import /path/to/ADEEvent_summary.py
  22. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Console tips

    (lldb) po [self.view recursiveDescription] $7 = 0x082a2c60 <UITableView: 0x8971000; frame = (0 0; 320 504); clipsToBounds = YES; autoresize = W+H; gestureRecognizers = <NSArray: 0x8184be0>; layer = <CALayer: 0x8184570>; contentOffset: {0, 0}> | <UITableViewCell: 0x8282900; frame = (0 176; 320 44); text = '2013-03-12 21:22:34 +0000'; autoresize = W; layer = <CALayer: 0x8282a30>> | | <UITableViewCellContentView: 0x8282a60; frame = (0 0; 300 43); gestureRecognizers = <NSArray: 0x8282c30>; layer = <CALayer: 0x8282ac0>> | | | <UILabel: 0x8282e50; frame = (10 0; 280 43); text = '2013-03-12 21:22:34 +0000'; clipsToBounds = YES; userInteractionEnabled = NO; layer = <CALayer: 0x8282ee0>> | | <UIButton: 0x8282c80; frame = (290 0; 30 43); opaque = NO; userInteractionEnabled = NO; layer = ... (lldb) po [[UIWindow keyWindow] recursiveDescription] $5 = 0x08273bc0 <UIWindow: 0x8181010; frame = (0 0; 320 568); layer = <UIWindowLayer: 0x81810e0>> | <UILayoutContainerView: 0xd06eed0; frame = (0 0; 320 568); autoresize = W+H; layer = <CALayer: 0xd071460>> | | <UINavigationTransitionView: 0xd09e850; frame = (0 0; 320 568); clipsToBounds = YES; autoresize = W +H; layer = <CALayer: 0xd09e920>> | | | <UIViewControllerWrapperView: 0x846e160; frame = (0 64; 320 504); autoresize = W+H; layer = <CALayer: 0x846e210>> ...
  23. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Tools •

    Network Link Conditioner • Charles • PonyDebugger • Deploymate
  24. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Network Link

    Conditioner • It’s a utility that enables you to simulate network conditions • To install just select Xcode > Open Developer Tool > More Developer Tools. You’ll be taken to Apple’s developer downloads site • Download “Hardware IO Tools for Xcode”
  25. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Charles •

    It’s a web debugging proxy • You can inspect, modify and record requests & responses • SSL Proxing (http://www.charlesproxy.com/ documentation/faqs/ssl-connections-from-within-iphone- applications/) http://www.charlesproxy.com/
  26. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly PonyDebugger •

    Network Traffic Debugger • Core Data Browser • It is a client library and gateway server combination that uses Chrome Developer Tools on your browser to debug your application's network traffic and managed object contexts. https://github.com/square/PonyDebugger
  27. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Deploymate •

    If using an API introduced later than your target OS but your app is targeting an older OS version, Xcode doesn't warn you about it • It helps identify unavailable, deprecated and obsolete API
  28. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Remote debugging

    • Apple Crash Reports • PLCrashReporter • TestFlight
  29. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Apple Crash

    Reports • For app published on App Store, you can acquire crash log from iTunes Connect and import it into Organizer for symbolication • To symbolicate a crash log, Xcode needs to have access to the matching application binary that was uploaded to the App Store, and the .dSYM file that was generated when that binary was built. This must be an exact match https://itunesconnect.apple.com
  30. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly PLCrashReporter •

    In-process CrashReporter framework for the iPhone and Mac OS X • Handles both uncaught Objective-C exceptions and fatal signals • Backtraces for all active threads are provided https://code.google.com/p/plcrashreporter/
  31. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly - (void)

    handleCrashReport { PLCrashReporter *crashReporter = [PLCrashReporter sharedReporter]; NSData *crashData; NSError *error; // Try loading the crash report crashData = [crashReporter loadPendingCrashReportDataAndReturnError: &error]; if (crashData == nil) { NSLog(@"Could not load crash report: %@", error); goto finish; } PLCrashReport *report = [[[PLCrashReport alloc] initWithData: crashData error: &error] autorelease]; if (report == nil) { NSLog(@"Could not parse crash report"); goto finish; } .... return; } // from UIApplicationDelegate protocol - (void) applicationDidFinishLaunching: (UIApplication *) application { PLCrashReporter *crashReporter = [PLCrashReporter sharedReporter]; NSError *error; // Check if we previously crashed if ([crashReporter hasPendingCrashReport]) [self handleCrashReport]; // Enable the Crash Reporter if (![crashReporter enableCrashReporterAndReturnError: &error]) NSLog(@"Warning: Could not enable crash reporter: %@", error); }
  32. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly TestFlight •

    Invite your testers, drop in the SDK and start uploading your builds. • Upload your builds and TestFlight takes care of the rest. Painless over-the-air distribution to your testers and distribution lists. • Complete tracking of your build, from distribution to sessions, checkpoints and crashes. https://testflightapp.com/
  33. Massimo Oliviero - [email protected] - www.massimooliviero.net - @maxoly Final Thoughts

    • Don’t use NSLog anymore ;) • Create your Xcode Behaviors • Breakpoints are your friends • LLDB is a promising youngster • Tools can save your life • The QA phase is essential
  34. Advanced iOS Debugging Thank you! Massimo Oliviero [email protected] http://www.massimooliviero.net follow

    me on twitter @maxoly http://www.slideshare.net/MassimoOliviero https://speakerdeck.com/massimooliviero