1. iOS Training
(Basics)
Gurpreet Singh
Sriram Viswanathan
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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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5. Introduction to Xcode
Xcode
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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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7. Understanding App Execution Flow
App execution flow
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8. Understanding App Execution Flow
Not running
Foreground
Inactive
Active
Background
Suspended
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9. App Delegate Methods
 application:willFinishLaunchingWithOptions
 application:didFinishLaunchingWithOptions
 applicationDidBecomeActive
 applicationWillResignAcitve
 applicationDidEnterBackground
 applicationWillEnterForeground
 applicationWillTerminate
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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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21. Objective C Basics
Example:
@interface Movie: NSObject {
NSString *name;
}
- (id) initWithString: (NSString *) movieName;
+ (Movie *) createMovieWithName: (NSString *) movieName;
@end
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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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25. Objective C Basics
Using Private Methods
@interface Movie: NSObject {
NSString *name;
}
- (id) initWithString: (NSString *) movieName;
+ (Movie *) createMovieWithName: (NSString *) movieName;
@end
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26. Objective C Basics
#import Movie.h;
@interface Movie (private)
- (id) initWithString: (NSString *) movieName;
@end
@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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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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28. Objective C Basics
Adding getter and setter methods
@interface Movie: NSObject {
NSString *name;
}
- (NSString *) name;
- (void) setName: (NSString *) movieName;
+ (Movie *) createMovieWithName: (NSString *) movieName;
@end
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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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31. Objective C Basics
Using @property and @synthesize directive
@interface Movie: NSObject {
NSString *name;
}
@property (nonatomic, strong) NSString *name;
- (NSString *) name;
- (void) setName: (NSString *) movieName;
+ (Movie *) createMovieWithName: (NSString *) movieName;
@end
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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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