Language (programming language) wars are overrated. As a professional/career software engineer, it is our job to learn fast, evolve and continually grow in the context of different languages and software paradigms. Learning Objective-C and iOS cocoa touch framework isn't as scary as people purport it to be. Ignore the critics, trust in your own abilities and dive into Objective-C if you need to build a mobile app for your company. Today.

1. LEARNING IOS
and hunting NSZombies in 3 weeks

2. About Me
@calvinchengx
• Chemical engineering from NUS
• Scientific Freezer Engineer for a local company
• Started my own software company, small team of 5 + some
interns
• Learned programming and web development along the way
• (web) appify scientific projects with universities
• Various consumer web apps python/django
• Attempted my own product start-up(s) including an app with
PhoneGap
• Currently working on an academic conference web app as a
product start-up, serving 3-4 conferences so far

3. 3 weeks? Why so kan-cheong??
:-)

4. “Teach yourself programming in Ten
Years (10,000 hours)
Peter Norvig, wrote in 2001
http://norvig.com/21-days.html

5. “A little learning is a dangerous thing.
Alexander Pope (1688 - 1744)

6. “Twas well observed by Lord Bacon, That a little
knowledge is apt to puff up, and make men giddy,
but a great share of it will set them right, and bring
them to low and humble thoughts of themselves.
Anonymous, A B (16th century)

7. “Ars longa, vita brevis,
occasio praeceps,
experimentum periculosm,
iudicium difficile
Hippocrates (c. 400 BC)

8. “To realize that you do not
understand is virtue; Not to realize
that you do not understand is defect.
Lao Tzu (c. 604 BC, Zhou Dynasty)

9. OK, OK, I GET IT!!! :-)
So are you, Mr Calvin Cheng,
going to change the title of this talk???

10. NOT QUITE :-)
Evolutionary superiority triumphs Technical superiority
Adopt a “Growth Mindset”

11. FIXED
You are great, or you aren’t
GROWTH
Anyone can master anything

15. WHY THIS MATTERS?
• Split 10,000 hours into very small projects/parts-of-a-big-project
• Push your boundary for each project and learn
• Learning != Muscle Memory
• Practice

16. Peter Norvig
tl;dr
• Get interested
• Program
• Talk with other programmers
• Work with other programmers
• Work after other programmers
• Learn at least 6 languages
• Figure out computer instruction execution, disk, memory
• Learn language standardization
• Get out from language standardization

17. Getting started with iOS/Objective-C
• Read blog posts and books; download and play with iOS apps
• Program with Tutorials; and your own creations
• Talk with people on http://facebook.com/groups/iosdevscout
• Work with colleagues or hack-alongs @ iOS Dev Scout meet-ups
• Work after iOS open source libraries on http://github.com
• Learn at least Python, Javascript (jQuery), golang, C, clojure (etc)
• Understand pointers/memory management, multi-threading etc
• Read best practices, learn programming methodologies, XP,
TDD, CI, CD and practice UI/UX.
• Repeat

18. Key Concepts in Objective-C & iOS
• Superset of C
• Message passing (small talk/obj-c) versus Method calls (c/c++)
• Delegation versus Inheritance

19. Message Passing
vs
Method Calling

20. • The difference between message passing and calling a
method is in the linking.
• c and c++ the function calls are linked at compile time
with the linker (except with virtual functions which
requires some runtime support).
• objective-c and smalltalk, you cannot guarantee what
functions will be run until runtime. The runtime
determines if an object actually implements the function
represented in the message. If it doesn't implement it, the
class will usually either forward the message onto another
object, or throw an exception.

21. • Overall, a message is the same thing as calling a
method directly, except the runtime finds the exact
function to be called instead of it being linked at compile
time.

22. Delegation
The real reason that you'd want to use delegation is that
the class you were designing has some resemblance to
another class, but isn't really enough like it that you'd call it
the same kind of thing.

23. Delegation
In c++, the only delegation that make sense is when you
are is a service (words ending with 'er', 'or', 'tory',
example HTMLLexER, JSONParsER, PrettyPrintER).
That is exactly what delegation sounds like. Delegating a
task to an expert class. (This could also result because the
lack of support for traits)
- Don Han

24. Delegation: An Example
Built-in iOS Your Custom
Object Object
Be a Delegate!
(dance)

25. Delegation: An Example
@protocol CLLocationManagerDelegate<NSObject> Built-in iOS
@optional
/*
* locationManager:didUpdateToLocation:fromLocation:
*
* Discussion:
* Invoked when a new location is available. oldLocation may be nil if there is no previous location
* available.
*/
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation;
...
@end

26. Delegation: An Example
Our Custom
class/object
// CurrentLocationViewController.h
// implements CLLocationManagerDelegate protocol
(be a delegate!)
#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
@interface CurrentLocationViewController : UIViewController <CLLocationManagerDelegate>
....
@end

27. Delegation: An Example
#import "CurrentLocationViewController.h"
Our Custom
class/object
@interface CurrentLocationViewController ()
- (void)updateLabels; (be a delegate!)
- (void)startLocationManager;
- (void)stopLocationManager;
- (void)configureGetButton;
- (NSString *)stringFromPlacemark:(CLPlacemark *)thePlacemark;
@end
@implementation CurrentLocationViewController {
CLGeocoder *geocoder;
CLPlacemark *placemark;
BOOL performingReverseGeocoding;
NSError *lastGeocodingError;
CLLocationManager *locationManager;
CLLocation *location;
NSError *lastLocationError;
BOOL updatingLocation;
}

28. Delegation: An Example
Our Custom
class/object
(be a delegate!)
...
- (void)startLocationManager
{
if ([CLLocationManager locationServicesEnabled]) {
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
[locationManager startUpdatingLocation];
updatingLocation = YES;
[self performSelector:@selector(didTimeOut:) withObject:nil afterDelay:60];
}
}
...

29. Delegation: An Example
Our Custom
class/object
(be a delegate!)
...
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:
(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
NSLog(@"didUpdateToLocation %@", newLocation);
if ([newLocation.timestamp timeIntervalSinceNow] < -5.0) {
return;
}
if (newLocation.horizontalAccuracy < 0) {
return;
} In CLLocationManagerDelegate.h
// This is new
CLLocationDistance distance = MAXFLOAT;
if (location != nil) {
distance = [newLocation distanceFromLocation:location];
}
...

30. Delegation: An Example
Built-in iOS
@protocol CLLocationManagerDelegate<NSObject>
@optional
/*
* locationManager:didUpdateToLocation:fromLocation:
*
* Discussion:
* Invoked when a new location is available. oldLocation may be nil if there is no
previous location
* available.
*/
- (void)locationManager:(CLLocationManager *)manager
didUpdateToLocation:(CLLocation *)newLocation
fromLocation:(CLLocation *)oldLocation;

31. Takeaway:
Not much use cases for subclass-ing.
Think in terms of
composition & delegation to
“specialized” pre-written code

32. Resources: iOS
• iOS Dev Scout
• iTunes University (Stanford, Paul Hegarty)
• Ray Wenderlich (Tutorials, Free & Paid)
• https://github.com/calvinchengx/BullsEye
• https://github.com/calvinchengx/Checklists
• https://github.com/calvinchengx/Calculator
• https://github.com/calvinchengx/MyLocations3
• https://bitbucket.org/calvinchengx/foloup2

33. People I learn with/from
many folks from......

36. Expand your programming perspectives. JOIN:
• iOS Dev Scout https://www.facebook.com/groups/iosdevscout/
• Pythonistas https://www.facebook.com/groups/pythonsg/
• PHP https://www.facebook.com/groups/sghypertextpreprocessors/
• Agile & DevOps https://www.facebook.com/groups/agiledevopssg/
• LittleHackers.com https://www.facebook.com/groups/littlehackers/
• golang SG https://www.facebook.com/groups/golanggonuts/
• RaspberryPi SG https://www.facebook.com/groups/
raspberrypisingapore/