2. Topics
Getting Started
Introduction to Xcode and Application settings
Understanding App execution flow
Introduction to Objective-C
Writing your First iPhone Application
Introduction to Interface Builder
Outlets and Actions
Storyboards
Using the iPhone/iPad Simulator
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3. Some Interesting Facts
What does ‘i’ stands for in iPhone?
iPhone 5 was world’s best selling smartphone in Q4 2012, iPhone
5 and iPhone 4S put together accounted for 1 in every 5
smartphones shipped in Q4.
Total iPhones sold till date – 250 million
Total iPads sold till date – 100 million
People spend $1 million / day in Apple App store.
App store has 8 lacs active apps as of March 2013
40 billion app downloads as of March 2013
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4. Topics
Getting Started
Introduction to Xcode and Application settings
Understanding App execution flow
Introduction to Objective-C
Writing your First iPhone Application
Introduction to Interface Builder
Outlets and Actions
Storyboards
Using the iPhone/iPad Simulator
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6. Topics
Getting Started
Introduction to Xcode and Application settings
Understanding App execution flow
Introduction to Objective-C
Writing your First iPhone Application
Introduction to Interface Builder
Outlets and Actions
Storyboards
Using the iPhone/iPad Simulator
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10. App Launch Cycle
User taps icon
main()
UIApplicationMain()
Load main UI File
First Initialization
application:willFinishLaunchingWithOptions
Restore UI state
Various methods
Final Initialization
application:didFinishLaunchingWithOptions
Activate the App
application:didBecomeActive
Event Loop
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Handle Events
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11. Topics
Getting Started
Introduction to Xcode and Application settings
Understanding App execution flow
Introduction to Objective-C
Writing your First iPhone Application
Introduction to Interface Builder
Outlets and Actions
Storyboards
Using the iPhone/iPad Simulator
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12. Objective C Basics
Objective C is layered on top of C language
Is a superset of C
Provides object-oriented capabilities
NeXT Software licensed Objective C in 1988
Apple acquired NeXT in 1996
Today it is the native language for developing applications for Mac OS X
and iOS
All of the syntax for non-object-oriented operations (including primitive
variables, expressions, function declarations) are identical to that of C
While the syntax for object-oriented features is an implementation of
messaging.
You might find its syntax a bit complex in starting but will get used to as
you progress.
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13. Objective C Basics
Creating objects
In other languages, you create objects like this:
object = new Class();
The same in Objective C will look like
object = [[Class alloc] init];
There might be some cases when you may want to pass some input while
creating objects.
In other languages you pass the input to the constructor like this:
object = new Class(2);
The same in Objective C you will do the same like this
object = [[Class alloc] initWithInt:2];
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14. Objective C Basics
Some points to note about objects in Objective C
All object variable are pointers
Object must be alloc'ed and init'ed
When you declare a variable to store an object you need to mention type of object it
will hold.
Class *object;
object = [[Class alloc] init];
Keyword id is just a way of saying any object
id object;
object = [[Class alloc] init];
id doesn't use pointer notation
Keyword nil just means no object
Class *object = nil;
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15. Objective C Basics
Declaring methods
A simple method declaration in other languages will look like
setX(n)
or
setX (int n);
or
void setX (int n);
The same in Objective C will look like
- (void) setX: (int) n;
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16. Objective C Basics
Method declaration explained
- (void) setX: (int)
n;
Method type:
+ = class method
- = instance method
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Return type
Method name
Argument type
Argument name
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17. Objective C Basics
Calling methods
A simple method call in other languages will look like
output = object.method();
output = object.method(inputParameter);
The same in Objective C will look like
output = [object method];
output = [object method:inputParameter];
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18. Objective C Basics
Nested method calls
In many languages, nested method or method calls look like this:
object.function1 ( object.function2() );
The same in Objective C will look like
[object function1:[object function2]];
e.g. [[Class alloc] init]
Multi-input methods
A simple multi-input method call in other languages will look like
object.setXAndY(3, 2);
The same in Objective C will look like
[object setX:3 andY:2];
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19. Objective C Basics
Multi-input methods explained
[object setX:3 andY:2]
Beginning Method
Call Syntax
Object of the Class
containing the method
First parameter
value
First named
parameter
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Ending Method
Call Syntax
Second parameter
value
Second named
parameter
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20. Objective C Basics
Creating classes
The specification of a class in Objective-C requires two distinct pieces: the
interface and the implementation.
The interface portion contains the class declaration and defines the instance
variables and methods associated with the class.
The interface is usually in a .h file.
The implementation portion contains the actual code for the methods of the class.
The implementation is usually in a .m file.
When you want to include header files in your source code, you typically use a
#import directive.
This is like #include, except that it makes sure that the same file is never
included more than once.
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22. Objective C Basics
#import Movie.h;
@implementation Movie
- (id) initWithString: (NSString *) movieName {
self = [super init];
if (self) {
name = movieName;
}
return self;
}
+ (Movie *) createMovieWithName: (NSString *) movieName {
return [[self alloc] initWithString: movieName];
}
@end
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Same as this (keyword) in other languages
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23. Objective C Basics
Some points to note about #import
Movie.m file includes Movie.h file.
Wherever we want to use Movie object we import Movie.h file (we never import
Movie.m file)
Use @class to avoid circular reference (class A needs to import class B and class
B needs to import class A).
@class B;
@interface A: NSObject
- (B*) calculateMyBNess;
@end
@class A;
@interface B: NSObject
- (A*) calculateMyANess;
@end
This concept is called forward declaration, tells compiler trust me there is class
called class B
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24. Objective C Basics
There are some issues in previous example (Movie Class)
By default all methods are public in objective C
By default all instance variables are private in objective C
What if I directly call initWithString instead of createMovieWithName?
We need to make initWithString private.
Secondly, what if I don’t know the movie name upfront and I want to create the
Movie object and then assign the name of movie later?
We have to provide public methods (getter and setter) to get and set the
movie name.
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27. Objective C Basics
Adding getter and setter methods
Note, in objective C, as per convention the getter method for a variable named ‘age’
is not ‘getAge’, in fact it is called as ‘age’ only.
But, the setter method for variable ‘age’ will be called as ‘setAge’.
So in our example, getter method will be movie.name and setter method will be
movie.setName
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29. Objective C Basics
…
@implementation Movie
- (NSString *) name {
return name;
}
- (void) setName: (NSString *) movieName {
if (![name isEqualToString: movieName]) {
name = movieName;
}
}
…
@end
Usage
Movie *myMovie = [[Movie alloc] init];
[myMovie setName:@”Dhoom”];
NSString *movieName = [myMovie name];
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30. Objective C Basics
Using @property and @synthesize directive
Adding getter / setter methods for all the instance variables can become a tedious
task.
Apple provide a simple way for this, you can use @property directive
Benefits
You do not have to write getter and setter methods yourself.
You can define the "assigning behavior" (namely copy, strong, weak,
nonatomic)
Keywords:
•
copy: The object is copied to the ivar when set
•
strong: The object is retained on set
•
weak: The object's pointer is assigned to the ivar when set and will be set to nil
automatically when the instance is deallocated
•
nonatomic: The accessor is not @synchronized (threadsafe), and therefore faster
•
atomic: The accessor is @synchronized (threadsafe), and therefore slower
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32. Objective C Basics
…
@implementation Movie
@synthesize name;
- (NSString *) name {
return name;
}
- (void) setName: (NSString *) movieName {
if (![name isEqualToString: movieName]) {
name = movieName;
}
}
…
@end
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33. Objective C Basics
To sum up:
NSString *name; - declares an instance variable 'name'
@property (nonatomic, strong) NSString *name; - declares the accessor methods for 'name'
@synthesize name; - implements the accessor methods for 'name'
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34. Objective C Basics
Using strings (NSString class)
NSString *movieName = @”Dhoom”;
The @ symbol
Ok, why does this funny @ sign show up all the time? Well, Objective-C is an extension of
the C-language, which has its own ways to deal with strings. To differentiate the new type of
strings, which are fully-fledged objects, Objective-C uses an @ sign.
A new kind of string
How does Objective-C improve on strings of the C language? Well, Objective-C strings are
Unicode strings instead of ASCII strings. Unicode-strings can display characters of just about
any language, such as Chinese, as well as the Roman alphabet.
A C string is simply a series of characters (a one-dimensional character array) that is nullterminated, whereas an NSString object is a complete object with class methods, instance
methods, etc.
Note: It is possible (but not recommended) to use C language strings in Objective C.
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35. Objective C Basics
Using ‘stringWithFormat’
NSString *movieName = [NSString stringWithFormat:@”Dhoom %d”, 2]; // Dhoom 2
Specifiers:
%d
%f
%@
Signed 32-bit integer (int)
64-bit floating-point number (double)
Objective-C object
Complete list of format specifiers is available here.
Introduction to NSLog
NSLog(@”Movie name is %@”, movieName);
Format specifiers same as ‘stringWithFormat’.
Used for debugging
Same as error_log in PHP or console.log in JavaScript
Note the use of round brackets unlike other method calls in objective C
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36. Objective C Basics
Using arrays (NSArray class)
Provide random access
The objects contained in an array do not all have to be of the same type.
Factory methods (static methods that build array from given parameters):
+ (id)array
Creates and returns an empty array
+ (id)arrayWithObjects
Creates and returns an array containing a given object
Lot of such factory methods available
Accessing the NSArray
- (BOOL)containsObject:(id)anObject
- (NSUInteger)count
- (id)lastObject
- (id)objectAtIndex:(NSUInteger)index
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Returns true if a given object is found in the array
Returns the size of the array
Returns the last object in the array
Returns the object at a given index.
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37. Objective C Basics
Introduction to NSMutableArray
NSArray is immutable (content of array cannot be modified without recreating it)
You can create mutable arrays (NSMutableArray) if you want to add or remove elements
after creating.
Additional functions to manipulate the array
insertObject:atIndex:
removeObjectAtIndex:
addObject:
removeLastObject
replaceObjectAtIndex:withObject:
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38. Objective C Basics
Introduction to NSDictionary
NSDictionary are like Maps and Hashes in other languages
Key-value pairs
It is an unordered collection of objects
Factory methods (static methods that build array from given parameters):
+ (id)dictionary
Creates and returns an empty dictionary
+ (id)dictionaryWithObjects: forKeys:
Creates and returns a dictionary containing entries
constructed from the contents of an array of keys
and an array of values
Lot of such factory methods available
Accessing the NSDictionary
– allKeys
– allValues
– objectForKey:
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Returns a new array containing the dictionary’s keys.
Returns a new array containing the dictionary’s values.
Returns the value associated with a given key.
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39. Objective C Basics
Introduction to NSMutableDictionary
Similar to NSArray, NSDictionary is also immutable
You can create mutable dictionary (NSMutableDictionary) if you want to add or remove
objects after creating.
Additional functions to manipulate the dictionary
setObject:forKey:
removeObjectForKey:
removeAllObjects:
removeObjectsForKeys:
Points to note:
NSArray and NSDictionary only store objects
So if you want to store numbers then you have to convert it to NSNumber
Use NSNull for empty values
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40. Topics
Getting Started
Introduction to Xcode and Application settings
Understanding App execution flow
Introduction to Objective-C
Writing your First iPhone Application
Introduction to Interface Builder
Outlets and Actions
Storyboards
Using the iPhone/iPad Simulator
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