Advanced iOS debbuging

Massimo Oliviero
Advanced iOS Debugging

massimo.oliviero@gmail.com

@maxoly #code12

Massimo Oliviero
Massimo Oliviero - massimo.oliviero@gmail.com - www.massimooliviero.net - @maxoly

Freelance Software Developer

Co-founder of #pragma mark http://pragmamark.org
Online
web http://www.massimooliviero.net
email massimo.oliviero@gmail.com
twitter @maxoly
slide http://www.slideshare.net/MassimoOliviero

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


Code

It all began...

NSLog(@"Array %@",
array);
NSLog(@"URL: %@", url);
NSLog(@"User: %@", user);

NSLog(@"Array: %@", array); NSLog(@"User:

NSLog(@"URL: %@", url);

NSLog(@"User: %@", user); NSLog(@"User: %@", user);

NSLog(@"Error :( %@", error);
NSLog(@"Error :( %@", error);
NSLog(@"User %@", NSLog(@"Count: %i", count);

user);
NSLog(@"Array: %@", array);
NSLog(@"Error :( %@",
error

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)

NSLog optimization

• Use convenient macro

• Use string conversions

• Try alternative frameworks

NSLog macro

MyGreatApp-preﬁx.pch
#if defined DEBUG
#define MYNSLog(s, ...) NSLog((@"%s [Line %d] " s), __PRETTY_FUNCTION__,
__LINE__, ##__VA_ARGS__)
#else
#define MYNSLog(s, ...)
#endif

TestViewController.m
- (void)viewDidLoad
{
[super viewDidLoad];

MYNSLog(@"message");
}

Console
-[TestViewController viewDidLoad] [Line 33] message

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)

String conversion functions

AdvanceDebuggingExample.m
CGPoint point = CGPointMake(10.5f, 12.3f);
NSLog(@"point: %@", NSStringFromCGPoint(point));

Console
AdvanceDebuggingExample[3050:c07] point: {10.5, 12.3}

String conversion functions

Returns a string formatted to contain the data from a
structure:
• NSStringFromCGAfﬁneTransform

• NSStringFromCGPoint

• NSStringFromCGRect

• NSStringFromCGSize

• NSStringFromUIEdgeInsets

• NSStringFromUIOffset

Try alternative frameworks

• CocoaLumberjack
https://github.com/robbiehanson/CocoaLumberjack

• NSLogger
https://github.com/fpillet/NSLogger

• DMLogger
https://github.com/malcommac/DMLogger


Demo


Xcode

Xcode

• Conﬁgure your Behaviors

• Print more information with Arguments

• Go beyond logging with Breakpoints


Behaviors

Xcode default Behaviors

Debugger bar

Xcode default Behaviors

Debugger
Navigator
Variables View Console

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)

Behaviors

Show Debug Navigator
When
Show debugger views
pauses

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


Arguments

Arguments

Product > Scheme > Edit Scheme > Arguments

Core Data Logging

-com.apple.CoreData.SQLDebug 1

Core Data and iCloud

-com.apple.coredata.ubiquity.logLevel 3


Breakpoints

Creating and editing breakpoint

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

Debugger Command Action

po variable

expr (void)NSLog(@”variable: %@”, variable)

breakpoint set -f ADEMasterViewController.m -l 83

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/


LLDB

Why LLDB

• Consistent Command Syntax

• Scriptability with Python

• Performance

• ...

LLDB Commands

(lldb) <command>

print object po [object]

print variable print [variable]

assign value expr [variable] = [value]

LLDB Commands

<noun> <verb> [-options [option-value]] [argument [argument...]]

set breakpoint breakpoint set -f [ﬁle] -l [line]

load script command script import ~/test.py

evaluate expression expr <expression>

Custom object, the problem

Custom object
@interface ADEEvent : NSObject

@property (nonatomic, strong) NSString *title;
@property (nonatomic, strong) NSDate *when; Init object
ADEEvent *event = [[ADEEvent alloc] init];
@end event.title = @"Codemotion Conference";
event.when = [NSDate date];

No summary for custom object

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

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

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>>
...


Tools

Tools

• Network Link Conditioner

• Charles

• PonyDebugger

• Deploymate

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”

Charles

http://www.charlesproxy.com/

• 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/)

PonyDebugger

https://github.com/square/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.

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


Remote

Remote debugging

• Apple Crash Reports

• PLCrashReporter

• TestFlight


Apple Crash Reports

Apple Crash Reports

https://itunesconnect.apple.com

• 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


PLCrashReporter

PLCrashReporter

https://code.google.com/p/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


- (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);

}


TestFlight

TestFlight

https://testﬂightapp.com/

• 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.


Final Thoughts

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


Thank you!
Massimo Oliviero
massimo.oliviero@gmail.com
http://www.massimooliviero.net

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

Advanced iOS debbuging

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