The document provides an introduction to Objective-C and iPhone programming, covering its syntax, object construction, and memory management techniques. It highlights the use of message passing, properties, and the relationship with Apple's Cocoa frameworks. Additionally, it suggests further resources for learning and expresses admiration for Steve Jobs' contributions to Apple and the development of iPhone apps.

1. A Quick and Dirty Intro to
Objective C and iPhone
Programming
…or how I stopped worrying and learned to love Steve Jobs

2. What we’re going to cover
• Objective C basics
• iPhone library basics
• Writing an app
• Worshipping Steve Jobs

3. Objective C
• Another way of doing object oriented C
• Superset of the C language
• Uses the Smalltalk idea of message
passing rather than method invocation
• May look familiar to Vision users

4. Objective C
• Created in the early ’80s
• Adopted by NeXT in 1988
• Apple bought NeXT in 1996 and adopted
objective C as the language behind Mac
OS X

5. HAIL STEVE
KING OF NeXT!

6. Message Passing
• Instead of calling a function we send
messages to our object;
Foo *myObject;
...
[myObject doThingsWithArg:argument];
Object Selector Argument

7. Function Declaration
• More new syntax:
-(void) doThingsWithArg:(int)anArg;
Method
“scope”
Return Type Selector Argument type Argument name

8. Class Definitions
• Split into two files
.h – header
.m - implementation

9. Foo.h:
@interface Foo : NSObject {
int anInt;
NSString *aString;
}
-(void) doThingsWithArg:(int)anArg;
@end

10. Foo.m:
#import “Foo.h”
@implementation Foo
-(void) doThingsWithArg:(int)anArg {
…
}
@end

11. Constructors
• 2 part construction of objects
– Allocation: Allocation selector is “alloc”
– Initialisation: Initialisation selector is custom,
but always starts with “init” by convention.
• Constructors return ‘id’ type
• Standard construction line looks like:
[[myObject alloc] init];

12. Foo.h:
@interface Foo : NSObject {
int anInt;
NSString *aString;
}
-(id) init;
-(id) initWithArg:(int)arg
andArg:(NSString*)arg2;
-(void) doThingsWithArg:(int)anArg;
@end

13. Foo.m:
#import “Foo.h”
@implentation Foo
-(id) init {
return self;
}
-(id) initWithArg:(int)arg
andArg:(NSString*)arg2
{
anInt=arg;
aString=arg2;
return self;
}
-(void) doThingsWithArg:(int)anArg {…}
@end

14. Properties
• New in Objective C 2
– Released a couple of years back
• Automatic construction of accessors
• Must be declared in header and
‘synthesised’ in implementation

15. Foo.h:
@interface Foo : NSObject {
int anInt;
NSString *aString;
}
-(id) init;
-(id) initWithArg:(int)arg
andArg:(NSString*)arg2;
-(void) doThingsWithArg:(int)anArg;
@property (readwrite,assign) int anInt;
@property (readwrite,copy) NSString *aString;
@end

16. Foo.m:
#import “Foo.h”
@implentation Foo
@synthesize anInt;
@synthesize aString;
-(id) init {
[super init];
return self;
}
-(id) initWithArg:(int)arg
andArg:(NSString*)arg2
{
[super init];
myInstanceVar=arg;
aString=arg2;
return self;
}
-(void) doThingsWithArg:(int)anArg {…}
@end

17. Using our new object
Foo *myObj1=[[Foo alloc] init];
Foo *myObj2=[[Foo alloc] initWithArg:1
andArg:@”Pie”];
[myObj1 doStuffWithArg:23];
NSLog(@”%d and %@”,myObj2.anInt, myObj2.aString);
//prints out “1 and Pie”
NSLog(@”%d and %@”, [myObj2 getAnInt],
[myObj2 getAString]);
//also prints out “1 and Pie”

18. What was that assign/copy stuff?
• Objective C has a number of ways of
doing memory management
– Garbage collector
• New and not used everywhere
– Allocation pools
• Baby version of garbage collection
– Reference counting
• Used everywhere, including with pools and
garbage collection

19. What was that assign/copy stuff?
• When you get an object its reference
count is 1
• Use “retain” to add one to the count
• Use “release” to drop one from the count
• When count hits zero the object is
destroyed
– Destructor method is called ‘dealloc’

21. What was that assign/copy stuff?
• In properties you get to say how you want
the reference counts done
– Assign is a simple assignment, no reference
counting
– Retain returns the pointer to an object and
ups the reference count by 1 (for non-objects
this just works like assign)
– Copy returns a copy of the object

22. Reference counting
• This talk is called “quick and dirty”
because that’s all the memory
management I’m mentioning
• I’m still not sure when to retain things as
whether things are copied/retained/etc is
generally based on function naming
conventions.
– Lame

23. iPhone
• The iPhone uses Objective C and a bunch
of Apple libraries
• For many apps you can just bolt together
library bits with a little bit of extra logic and
data

24. The Steve says “LETS MAKE AN APP”

25. Going Further
• THE Cocoa programming book seems to
be:
Cocoa Programming for Mac OS X by Aaron Hillegass

26. Going Further
• Series of talks by Evan Doll and Alan
Cannistraro up on iTunes U
• Talks done at Stanford University in
Summer 2009 for the 2nd
year of their
iPhone programming course
• Missing some iPhone OS 3 features, but
very good.

27. Going Further
• Buy a Mac
• Make The Steve pleased
• Wear rollneck sweaters
• Conform
• Conform
• Conform
• Conform
• Conform
• Conform
• Conform