Beginningi os part1-bobmccune

Beginning iOS
Development

http://bobmccune.com

Monday, March 19, 12

Agenda
Beginning iOS Development
• Understanding the Tools
• Objective-C Crash Course
• Using Cocoa Touch


iOS SDK Tools


Xcode


Xcode
• Apple’s IDE for creating Mac and iOS apps
• Provides visual front end to LLVM and LLDB
• Hub of development process:
Editing UI Design
Building Testing
Refactoring Model Design
Debugging Deployment
API Doc Integration Project Conﬁguration


iOS Simulator


iOS Simulator
• Device simulator, runs on your desktop
• Both iPhone and iPad (retina, non-retina)
• Faster code, build, test cycle
• Test behaviors: rotation, shake, multi-touch
• Easier testing of exceptional conditions
• iOS Simulator != iOS Device:
• No memory or CPU limits
• Not all APIs and capabilities available

Instruments


Instruments

• Dynamic tracing and proﬁling tool
• Uses digital audio workstation-like interface
• Large library of standard instruments
• Core Animation, Leaks, Automation, etc.
• The ultra geeky can build custom instruments


Hands-On Tour


Objective-C


Agenda
Objective-C Essentials
• Overview of Objective-C
• Understanding Classes and Objects
• Methods, Messages, and Properties
• Protocols


Objective-C
The old, new hotness
• Strict superset of ANSI C
• Object-oriented extensions
• Additional syntax and types
• Dynamic, Object-Oriented Language:
• Dynamic Typing
• Dynamic Binding
• Dynamic Loading


Creating Classes


Creating Classes
The Blueprint
• Objective-C classes are separated into an
interface and an implementation.
• Usually defined in separate .h and .m files

•Defines the •Defines the actual
programming implementation
interface code

•Can define
object instance •Implement one or
variables more initializers to
properly initialize
an object instance


Deﬁning the Interface
@interface BankAccount : NSObject {
float accountBalance;
NSString *accountNumber;
}

- (float)withDraw:(float)amount;
- (void)deposit:(float)amount;
@end


Deﬁning the Implementation
#import "BankAccount.h"

@implementation BankAccount

- (id)init {
self = [super init];
return self;
}

- (float)withdraw:(float)amount {
// calculate valid withdrawal
return amount;
}

- (void)deposit:(float)amount {
// record transaction
}
@end


Defining Methods
Understanding the Syntax
• Class methods
• Prefixed with a +
• Tied to class, not instance
• Instance Methods
• Instance methods prefix with a -
• Modifies state of an object instance

- (NSString *)description;


Deﬁning Methods
• Class methods

- (BOOL)respondsToSelector:(SEL)aSelector;


Deﬁning Methods
• Class methods
+ (void)transitionWithView:(UIView *)view
duration:(NSTimeInterval)duration
options:(UIViewAnimationOptions)options
animations:(void (^)(void))animations
completion:(void (^)(BOOL finished))completion;


self and super
Talking to yourself
• Methods have implicit reference to owning
object called self
• Additionally have access to superclass
methods using super
-(id)init {
self = [super init];
if (self) {
// do initialization
}
return self;
}


Working with Objects


Two-Stage Creation
• NSObject defines class method called alloc
• Dynamically allocates memory for object
• Returns new instance of receiving class
BankAccount *account = [BankAccount alloc];

• NSObject defines instance method init
• Implemented by subclasses to initialize instance after memory
for it has been allocated
• Subclasses commonly define several initializers
account = [account init];

• alloc and init calls should always nested into single line
BankAccount *account = [[BankAccount alloc] init];


Messages
Communicating with Objects
• Methods are invoked by passing messages
• Methods are never directly invoked
• Messages dynamically bound to method
implementations at runtime
• Simple messages take the form:
•

[object message];

• Can pass one or more arguments:
•

[object methodWithArg1:arg1 arg2:arg2];


Messaging an Object
NSMutableDictionary *person =
[NSMutableDictionary dictionary];

[person setObject:@"Joe Smith" forKey:@"name"];

NSString *address = @"123 Street";
NSString *house =
[address substringWithRange:NSMakeRange(0, 3)];
[person setObject:house forKey:@"houseNumber"];

NSArray *children =
[NSArray arrayWithObjects:@"Jack", @"Susie", nil];

[person setObject:children forKey:@"children"];


Declared Properties


Declared Properties
Simplifying Accessors
• Most common methods we write are accessors
• Objective-C can automatically generate accessors
• Much less verbose, less error prone
• Highly configurable
• Declared properties are defined in two parts:
• @property definition in the interface
• @synthesize statement in the implementation


Declaring Properties
@property (attributes) type variable;

Attribute Impacts
nonatomic Concurrency

readonly/readwrite Mutability

strong/copy/
Storage
weak/assign

getter/setter API



Attribute Impacts


strong/copy/
Storage
weak/assign

getter/setter API

@property (readonly) BOOL active;


Attribute Impacts


strong/copy/
Storage
weak/assign

getter/setter API

@property (nonatomic, readonly) BOOL active;



Attribute Impacts


strong/copy/
Storage
weak/assign

getter/setter API

@property (nonatomic, strong) NSDate *activeDate;



Attribute Impacts


strong/copy/
Storage
weak/assign

getter/setter API

@property (readonly, getter=isValid) BOOL valid;


Deﬁning the Interface

@interface BankAccount : NSObject

@property (nonatomic, copy) NSString *accountNumber;
@property (nonatomic, strong) NSDecimalNumber *balance;
@property (readonly, strong) NSDecimalNumber *fees;
@property (getter=isCurrent) BOOL accountCurrent;

@end


Synthesizing Properties
Generating the Accessors

@implementation BankAccount

@synthesize accountNumber = _accountNumber;
@synthesize balance = _balance;
@synthesize fees = _fees;
@synthesize accountCurrent = _accountCurrent;

@end


Accessing Properties
• Generated properties are standard methods
• Accessed through normal messaging syntax
[object property];
[object setProperty:newValue];

• Objective-C property access via dot notation
object.property;
object.property = newValue;

Dot notation is just syntactic sugar. Still uses accessor
methods. Doesn't get/set values directly.


Protocols


Protocols
Object-Oriented Contracts
• Abstract methods to be implemented
• Methods are not tied to a speciﬁc class
• Analogous to C# and Java interfaces
• Useful in deﬁning:
• Capturing similarities among classes that aren't
hierarchically related
• Declaring an interface while hiding its particular
class
• Delegate callback methods


Deﬁning a Protocol
NSCoding
* NSCoding deﬁned in Foundation Framework

@protocol NSCoding

- (void)encodeWithCoder:(NSCoder *)aCoder;
- (id)initWithCoder:(NSCoder *)aDecoder;

@end


Adopting a Protocol
Conforming to the Contract

@interface User : NSObject <NSCoding>

@property (nonatomic, copy) NSString *username;
@property (nonatomic, copy) NSString *password;

@end


Adopting a Protocol
Conforming to the Contract
@implementation User

-(id)initWithCoder:(NSCoder *)coder {
if (self = [super init]) {
self.username = [coder decodeObjectForKey:@"username"];
self.password = [coder decodeObjectForKey:@"password"];
}
return self;
}

-(void)encodeWithCoder:(NSCoder *)coder {
[coder encodeObject:self.username forKey:@"username"];
[coder encodeObject:self.username forKey:@"password"];
}

@end


Time to Code!


Using Cocoa Touch


Cocoa Touch
Foundation Framework

• Core framework for non-UI functionality
• Operating System Classes
• threading, archiving, ﬁlesystem
• Collections
• Common collection types: arrays, dictionaries, sets
• Networking support
• XML Processing


Cocoa Touch
UIKit Framework

• Framework for building iOS user interfaces
• User Interface Elements
• Tables, buttons, images, etc.
• Views and View Controllers
• Multitouch Event Handling
• High-level Drawing Routines


Understanding MVC
Model,View, Controller

Model View

Controller


UIView
The “V” in MVC
• Base class for iOS user interface components
• Drawing and animation
• Layout and subview management
• Multitouch event handling
• Xcode’s Interface Builder used to build UI
• Archived version of UI stored in XIB/NIB ﬁle
• Dynamically loaded at runtime by controller
• Can be created programmatically


UIViewController
The “C” in MVC
• The heart of every iOS app
• Provides the “glue code” between the model
and view
• Responsible for managing the view hierarchy
and lifecycle
• Key view lifecycle methods:
- (void)loadView;
- (void)viewDidLoad;
- (void)viewDidUnload;


UIViewController: View Loading
controller.view

View Controller

Is view nil?

View loadView viewDidLoad

1) Overridden
2) Loaded from NIB
3) Return empty UIView


View Unloading
Dealing with low memory conditions
• didReceiveMemoryWarning
• Called by OS when low memory encountered
• If possible, will release controller’s view
• Can override, but must call super
• viewDidUnload invoked if root view released
• Override to release anything that can be
recreated in loadView/viewDidLoad


Display-related Callbacks
viewWillAppear
• Called immediately prior to being presented
viewDidAppear
• Called upon view being added to window
viewWillDisappear
• Called immediately before view is removed
from window or is covered by another view
viewDidDisappear
• Called after view is removed from window or
is covered by another view


Outlets and Actions
Wiring the View and View Controller
• Provides metadata to Interface Builder to
allow connections between objects
• IBOutlet
• Property reference to XIB/NIB objects
• Null-deﬁned C macro
• IBAction
• Used by Interface Builder to determine available
actions
• Void-deﬁned C macro


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